 Photons emitted in a coherent beam from a laser |
|
| Composition | Elementary particle |
|---|---|
| Family | Boson |
| Group | Gauge boson |
| Interaction | Electromagnetic |
| Theorized | Albert Einstein (1905–17) |
| Symbol | γ or hν |
| Mass | 0[1] |
| Mean lifetime | Stable[2] |
| Electric charge | 0 |
| Spin | 1[1] |
In physics, the photon is the elementary particle responsible for electromagnetic phenomena. In Physics, coherence is a property of waves that enables stationary (i A laser is a device that emits Light ( Electromagnetic radiation) through a process called Stimulated emission. In Particle physics, an elementary particle or fundamental particle is a particle not known to have substructure that is it is not known to be made In Particle physics, bosons are particles which obey Bose-Einstein statistics; they are named after Satyendra Nath Bose and Albert Einstein In Particle physics, gauge bosons are Bosonic particles that act as carriers of the fundamental forces of nature In Physics, a fundamental interaction or fundamental force is a mechanism by which particles interact with each other and which cannot be explained in terms Electromagnetism is the Physics of the Electromagnetic field: a field which exerts a Force on particles that possess the property of Albert Einstein ( German: ˈalbɐt ˈaɪ̯nʃtaɪ̯n; English: ˈælbɝt ˈaɪnstaɪn (14 March 1879 – 18 April 1955 was a German -born theoretical Given an assembly of elements the number of which decreases ultimately to zero the lifetime (also called the mean lifetime) is a certain number that characterizes the rate The elementary charge, usually denoted e, is the Electric charge carried by a single Proton, or equivalently the negative of the electric charge carried In Quantum mechanics, spin is a fundamental property of atomic nuclei, Hadrons and Elementary particles For particles with non-zero spin Physics (Greek Physis - φύσις in everyday terms is the Science of Matter and its motion. In Particle physics, an elementary particle or fundamental particle is a particle not known to have substructure that is it is not known to be made Electromagnetism is the Physics of the Electromagnetic field: a field which exerts a Force on particles that possess the property of It is the carrier of electromagnetic radiation of all wavelengths, including gamma rays, X-rays, ultraviolet light, visible light, infrared light, microwaves, and radio waves. In Particle physics, the Quantum field theory called the Standard Model describes the strong, weak and electromagnetic Fundamental Electromagnetic radiation takes the form of self-propagating Waves in a Vacuum or in Matter. In Physics wavelength is the distance between repeating units of a propagating Wave of a given Frequency. Gamma rays (denoted as &gamma) are a form of Electromagnetic radiation or light emission of frequencies produced by sub-atomic particle interactions X-radiation (composed of X-rays) is a form of Electromagnetic radiation. Ultraviolet ( UV) light is Electromagnetic radiation with a Wavelength shorter than that of Visible light, but longer than X-rays Infrared ( IR) radiation is Electromagnetic radiation whose Wavelength is longer than that of Visible light, but shorter than that of Microwaves are electromagnetic waves with Wavelengths ranging from 1 mm to 1 m or frequencies between 0 Radio is the transmission of signals by Modulation of electromagnetic waves with frequencies below those of visible Light. The photon differs from many other elementary particles, such as the electron and the quark, in that it has zero rest mass;[3] therefore, it travels (in a vacuum) at the speed of light, c. The electron is a fundamental Subatomic particle that was identified and assigned the negative charge in 1897 by J In Physics, a quark (kwɔrk kwɑːk or kwɑːrk is a type of Subatomic particle. This vacuum means "absence of matter" or "an empty area or space" for the cleaning appliance see Vacuum cleaner. Like all quanta, the photon has both wave and particle properties (“wave–particle duality”). In Physics and Chemistry, wave–particle duality is the concept that all Matter and Energy exhibits both Wave -like and Photons show wave-like phenomena, such as refraction by a lens and destructive interference when reflected waves cancel each other out; however, as a particle, it can only interact with matter by transferring the amount of energy
where h is Planck's constant, c is the speed of light, and λ is its wavelength. Refraction is the change in direction of a Wave due to a change in its Speed. The Planck constant (denoted h\ is a Physical constant used to describe the sizes of quanta. This is different from a classical wave, which may gain or lose arbitrary amounts of energy. For visible light the energy carried by a single photon is around 4×10–19 joules; this energy is just sufficient to excite a single molecule in a photoreceptor cell of an eye, thus contributing to vision. The joule (written in lower case ˈdʒuːl or /ˈdʒaʊl/ (symbol J) is the SI unit of Energy measuring heat, Electricity A photoreceptor, or photoreceptor cell, is a specialized type of Neuron (nerve cell found in the Eye 's Retina that is capable of Eyes are organs that detect Light, and send signals along the Optic nerve to the visual areas of the brain In Psychology, visual perception is the ability to interpret information from Visible light reaching the Eyes The resulting Perception is also [4]
Apart from having energy, a photon also carries momentum and has a polarization. In Classical mechanics, momentum ( pl momenta SI unit kg · m/s, or equivalently N · s) is the product Polarization ( ''Brit'' polarisation) is a property of Waves that describes the orientation of their oscillations It follows the laws of quantum mechanics, which means that often these properties do not have a well-defined value for a given photon. Quantum mechanics is the study of mechanical systems whose dimensions are close to the Atomic scale such as Molecules Atoms Electrons Rather, they are defined as a probability to measure a certain polarization, position, or momentum. For example, although a photon can excite a single molecule, it is often impossible to predict beforehand which molecule will be excited.
The above description of a photon as a carrier of electromagnetic radiation is commonly used by physicists. However, in theoretical physics, a photon can be considered as a mediator for any type of electromagnetic interactions, including magnetic fields and electrostatic repulsion between like charges.
The modern concept of the photon was developed gradually (1905–17) by Albert Einstein[5][6][7][8] to explain experimental observations that did not fit the classical wave model of light. Albert Einstein ( German: ˈalbɐt ˈaɪ̯nʃtaɪ̯n; English: ˈælbɝt ˈaɪnstaɪn (14 March 1879 – 18 April 1955 was a German -born theoretical The electromagnetic wave equation is a second-order partial differential equation that describes the propagation of Electromagnetic waves through a medium In particular, the photon model accounted for the frequency dependence of light's energy, and explained the ability of matter and radiation to be in thermal equilibrium. Matter is commonly defined as being anything that has mass and that takes up space. Electromagnetic radiation takes the form of self-propagating Waves in a Vacuum or in Matter. In Thermodynamics, a thermodynamic system is said to be in thermodynamic equilibrium when it is in thermal equilibrium Mechanical equilibrium, and Other physicists sought to explain these anomalous observations by semiclassical models, in which light is still described by Maxwell's equations, but the material objects that emit and absorb light are quantized. In Classical electromagnetism, Maxwell's equations are a set of four Partial differential equations that describe the properties of the electric Although these semiclassical models contributed to the development of quantum mechanics, further experiments proved Einstein's hypothesis that light itself is quantized; the quanta of light are photons. Quantum mechanics is the study of mechanical systems whose dimensions are close to the Atomic scale such as Molecules Atoms Electrons In Physics, quantization is a procedure for constructing a Quantum field theory starting from a classical field theory.
The photon concept has led to momentous advances in experimental and theoretical physics, such as lasers, Bose–Einstein condensation, quantum field theory, and the probabilistic interpretation of quantum mechanics. A laser is a device that emits Light ( Electromagnetic radiation) through a process called Stimulated emission. A Bose–Einstein condensate (BEC is a State of matter of Bosons confined in an external Potential and cooled to Temperatures very near to In quantum field theory (QFT the forces between particles are mediated by other particles In Quantum mechanics, a probability amplitude is a complex -valued function that describes an uncertain or unknown quantity According to the Standard Model of particle physics, photons are responsible for producing all electric and magnetic fields, and are themselves the product of requiring that physical laws have a certain symmetry at every point in spacetime. The Standard Model of Particle physics is a theory that describes three of the four known Fundamental interactions together with the Elementary particles Particle physics is a branch of Physics that studies the elementary constituents of Matter and Radiation, and the interactions between them In Physics, the space surrounding an Electric charge or in the presence of a time-varying Magnetic field has a property called an electric field (that can In Physics, a magnetic field is a Vector field that permeates space and which can exert a magnetic force on moving Electric charges Symmetry in physics refers to features of a Physical system that exhibit the property of Symmetry —that is under certain transformations, aspects of these SpaceTime is a patent-pending three dimensional graphical user interface that allows end users to search their content such as Google Google Images Yahoo! YouTube eBay Amazon and RSS The intrinsic properties of photons—such as charge, mass and spin—are determined by the properties of this gauge symmetry. Electric charge is a fundamental conserved property of some Subatomic particles which determines their Electromagnetic interaction. In Quantum mechanics, spin is a fundamental property of atomic nuclei, Hadrons and Elementary particles For particles with non-zero spin Gauge theory is a peculiar Quantum field theory where the Lagrangian is invariant under certain transformations
The concept of photons is applied to many areas such as photochemistry, high-resolution microscopy, and measurements of molecular distances. Photochemistry, a sub-discipline of Chemistry, is the study of the interactions between Atoms, small Molecules, and light (or Electromagnetic radiation Two-photon excitation microscopy is a Fluorescence imaging technique that allows imaging living tissue up to a depth of one millimeter Förster resonance energy transfer (abbreviated FRET) also known as Fluoresence resonance energy transfer or resonance energy transfer ( RET Recently, photons have been studied as elements of quantum computers and for sophisticated applications in optical communication such as quantum cryptography. A quantum computer is a device for Computation that makes direct use of distinctively Quantum mechanical Phenomena, such as superposition Optical communication is any form of Telecommunication that uses Light as the transmission medium Quantum cryptography, or quantum key distribution (QKD uses Quantum mechanics to guarantee secure communication
Nomenclature
The photon was originally called a “light quantum” (das Lichtquant) by Albert Einstein. Albert Einstein ( German: ˈalbɐt ˈaɪ̯nʃtaɪ̯n; English: ˈælbɝt ˈaɪnstaɪn (14 March 1879 – 18 April 1955 was a German -born theoretical [5] The modern name “photon” derives from the Greek word for light, φῶς, (transliterated phôs), and was coined in 1926 by the physical chemist Gilbert N. Lewis, who published a speculative theory[9] in which photons were “uncreatable and indestructible”. Greek (el ελληνική γλώσσα or simply el ελληνικά — "Hellenic" is an Indo-European language, spoken today by 15-22 million people mainly Gilbert Newton Lewis ( October 23, 1875 - March 23, 1946) was a famous American physical chemist known for the discovery Although Lewis' theory was never accepted—being contradicted by many experiments—his new name, photon, was adopted immediately by most physicists. Isaac Asimov credits Arthur Compton with defining quanta of light as photons in 1927. Isaac Asimov (c January 2 1920 &ndash April 6 1992 ˈaɪzək ˈæzɪmʌv originally Исаак Озимов but now transcribed into Russian as, was a Russian Arthur Holly Compton (September 10 1892 &ndash March 15 1962 was an American physicist and Nobel laureate in physics for his discovery of the Compton effect [10][11]
In physics, a photon is usually denoted by the symbol γ, the Greek letter gamma. The Greek alphabet (Ελληνικό αλφάβητο is a set of twenty-four letters that has been used to write the Greek language since the late 9th or early Gamma (uppercase &Gamma, lowercase γ Γάμμα is the third letter of the Greek alphabet. This symbol for the photon probably derives from gamma rays, which were discovered and named in 1900 by Villard[12][13] and shown to be a form of electromagnetic radiation in 1914 by Rutherford and Andrade. Gamma rays (denoted as &gamma) are a form of Electromagnetic radiation or light emission of frequencies produced by sub-atomic particle interactions Paul Ulrich Villard (1860 &ndash 13 January 1934) was a French Chemist and Physicist, born in Saint-Germain-au-Mont-d'Or 28th of September 1860 Electromagnetic radiation takes the form of self-propagating Waves in a Vacuum or in Matter. Ernest Rutherford 1st Baron Rutherford of Nelson, OM, PC, FRS (30 August 1871 – 19 October 1937 was a New Zealand Physicist Edward Neville da Costa Andrade FRS ( December 27, 1887 - June 6, 1971) was an English Physicist, writer and [14] In chemistry and optical engineering, photons are usually symbolized by hν, the energy of a photon, where h is Planck's constant and the Greek letter ν (nu) is the photon's frequency. Chemistry (from Egyptian kēme (chem meaning "earth") is the Science concerned with the composition structure and properties Optical engineering is the field of study that focuses on applications of Optics. The Planck constant (denoted h\ is a Physical constant used to describe the sizes of quanta. The Greek alphabet (Ελληνικό αλφάβητο is a set of twenty-four letters that has been used to write the Greek language since the late 9th or early Nu (uppercase Ν, lowercase ν; Νι Ni is the 13th letter of the Greek alphabet. Frequency is a measure of the number of occurrences of a repeating event per unit Time. Much less commonly, the photon can be symbolized by hf, where its frequency is denoted by f.
Physical properties
- See also: Special relativity
The photon is massless,[3] has no electric charge[15] and does not decay spontaneously in empty space. Special relativity (SR (also known as the special theory of relativity or STR) is the Physical theory of Measurement in Inertial Electric charge is a fundamental conserved property of some Subatomic particles which determines their Electromagnetic interaction. A photon has two possible polarization states and is described by exactly three continuous parameters: the components of its wave vector, which determine its wavelength λ and its direction of propagation. Polarization ( ''Brit'' polarisation) is a property of Waves that describes the orientation of their oscillations A wave vector is a vector representation of a Wave. The wave vector has magnitude indicating Wavenumber (reciprocal of Wavelength) and the The photon is the gauge boson for electromagnetism, and therefore all other quantum numbers—such as lepton number, baryon number, or strangeness—are exactly zero. In Particle physics, gauge bosons are Bosonic particles that act as carriers of the fundamental forces of nature Electromagnetism is the Physics of the Electromagnetic field: a field which exerts a Force on particles that possess the property of In High energy physics, the lepton number is the number of Leptons minus the number of antileptons In Particle physics, the baryon number is an approximate conserved Quantum number of a system
Photons are emitted in many natural processes, e. g. , when a charge is accelerated, during a molecular, atomic or nuclear transition to a lower energy level, or when a particle and its antiparticle are annihilated. Electron-positron annihilation occurs when an Electron and a Positron (the electron's anti-particle) collide Photons are absorbed in the time-reversed processes which correspond to those mentioned above: for example, in the production of particle–antiparticle pairs or in molecular, atomic or nuclear transitions to a higher energy level. T Symmetry is the symmetry of physical laws under a Time reversal transformation &mdash T t \mapsto -t See also Electron-positron annihilation Meitner–Hupfeld effect Pair instability supernova
In empty space, the photon moves at c (the speed of light) and its energy E and momentum p are related by E = cp, where p is the magnitude of the momentum. In Physics and other Sciences energy (from the Greek grc ἐνέργεια - Energeia, "activity operation" from grc ἐνεργός In Classical mechanics, momentum ( pl momenta SI unit kg · m/s, or equivalently N · s) is the product For comparison, the corresponding equation for particles with a mass m is E2 = c2p2 + m2c4, as shown in special relativity. Mass is a fundamental concept in Physics, roughly corresponding to the Intuitive idea of how much Matter there is in an object Special relativity (SR (also known as the special theory of relativity or STR) is the Physical theory of Measurement in Inertial
The energy and momentum of a photon depend only on its frequency ν or, equivalently, its wavelength λ
and consequently the magnitude of the momentum is
where 
(known as Dirac's constant or Planck's reduced constant); k is the wave vector (with the wave number k = 2π / λ as its magnitude) and ω = 2πν is the angular frequency. Frequency is a measure of the number of occurrences of a repeating event per unit Time. In Physics wavelength is the distance between repeating units of a propagating Wave of a given Frequency. The Planck constant (denoted h\ is a Physical constant used to describe the sizes of quanta. A wave vector is a vector representation of a Wave. The wave vector has magnitude indicating Wavenumber (reciprocal of Wavelength) and the Do not confuse with Angular velocity In Physics (specifically Mechanics and Electrical engineering) angular frequency Notice that k points in the direction of the photon's propagation. The photon also carries spin angular momentum that does not depend on its frequency. In Quantum mechanics, spin is a fundamental property of atomic nuclei, Hadrons and Elementary particles For particles with non-zero spin [16] The magnitude of its spin is 
and the component measured along its direction of motion, its helicity, must be 
. In Particle physics, helicity is the projection of the spin \vec S onto the direction of momentum \hat p: h = \vec These two possible helicities correspond to the two possible circular polarization states of the photon (right-handed and left-handed). In Electrodynamics, circular polarization (also circular polarisation) of Electromagnetic radiation is a Polarization such that the tip of the
To illustrate the significance of these formulae, the annihilation of a particle with its antiparticle must result in the creation of at least two photons for the following reason. Electron-positron annihilation occurs when an Electron and a Positron (the electron's anti-particle) collide In the center of mass frame, the colliding antiparticles have no net momentum, whereas a single photon always has momentum. See also Inertial frame A frame of reference in Physics, may refer to a Coordinate system or set of axes within which to Hence, conservation of momentum requires that at least two photons are created, with zero net momentum. In Classical mechanics, momentum ( pl momenta SI unit kg · m/s, or equivalently N · s) is the product The energy of the two photons—or, equivalently, their frequency—may be determined from conservation of four-momentum. In Physics, a conservation law states that a particular measurable property of an isolated Physical system does not change as the system evolves Seen another way, the photon can be considered as its own antiparticle. The reverse process, pair production, is the dominant mechanism by which high-energy photons such as gamma rays lose energy while passing through matter. See also Electron-positron annihilation Meitner–Hupfeld effect Pair instability supernova Gamma rays (denoted as &gamma) are a form of Electromagnetic radiation or light emission of frequencies produced by sub-atomic particle interactions
The classical formulae for the energy and momentum of electromagnetic radiation can be re-expressed in terms of photon events. Electromagnetic radiation takes the form of self-propagating Waves in a Vacuum or in Matter. For example, the pressure of electromagnetic radiation on an object derives from the transfer of photon momentum per unit time and unit area to that object, since pressure is force per unit area and force is the change in momentum per unit time. Radiation pressure is the Pressure exerted upon any surface exposed to Electromagnetic radiation. In Classical mechanics, momentum ( pl momenta SI unit kg · m/s, or equivalently N · s) is the product
Historical development
In most theories up to the eighteenth century, light was pictured as being made up of particles. Since particle models cannot easily account for the refraction, diffraction and birefringence of light, wave theories of light were proposed by René Descartes (1637),[17] Robert Hooke (1665),[18] and Christian Huygens (1678);[19] however, particle models remained dominant, chiefly due to the influence of Isaac Newton. Refraction is the change in direction of a Wave due to a change in its Speed. Diffraction is normally taken to refer to various phenomena which occur when a wave encounters an obstacle Birefringence, or double refraction, is the decomposition of a ray of Light into two rays (the ordinary ray and the extraordinary ray Robert Hooke, FRS (18 July 1635 – 3 March 1703 was an English Natural philosopher and Polymath who played an important role in the Christiaan Huygens (ˈhaɪgənz in English ˈhœyɣəns in Dutch) ( April 14, 1629 &ndash July 8, 1695) was a Dutch Sir Isaac Newton, FRS (ˈnjuːtən 4 January 1643 31 March 1727) Biography Early years See also Isaac Newton's early life and achievements [20] In the early nineteenth century, Thomas Young and August Fresnel clearly demonstrated the interference and diffraction of light and by 1850 wave models were generally accepted. Thomas Young (13 June 1773 &ndash 10 May 1829 was an English Polymath who contributed to the scientific understanding of vision, Light In physics interference is the addition ( superposition) of two or more Waves that result in a new wave pattern [21] In 1865, James Clerk Maxwell's prediction[22] that light was an electromagnetic wave—which was confirmed experimentally in 1888 by Heinrich Hertz's detection of radio waves[23]—seemed to be the final blow to particle models of light. James Clerk Maxwell (13 June 1831 &ndash 5 November 1879 was a Scottish mathematician and theoretical physicist. In Classical electromagnetism, Maxwell's equations are a set of four Partial differential equations that describe the properties of the electric Heinrich Rudolf Hertz ( February 22, 1857 – January 1, 1894) was a German physicist who clarified and expanded the electromagnetic theory Radio is the transmission of signals by Modulation of electromagnetic waves with frequencies below those of visible Light.
The Maxwell wave theory, however, does not account for all properties of light. The electromagnetic wave equation is a second-order partial differential equation that describes the propagation of Electromagnetic waves through a medium The Maxwell theory predicts that the energy of a light wave depends only on its intensity, not on its frequency; nevertheless, several independent types of experiments show that the energy imparted by light to atoms depends only on the light's frequency, not on its intensity. In Physics, intensity is a measure of the time-averaged Energy Flux. Frequency is a measure of the number of occurrences of a repeating event per unit Time. For example, some chemical reactions are provoked only by light of frequency higher than a certain threshold; light of frequency lower than the threshold, no matter how intense, does not initiate the reaction. Photochemistry, a sub-discipline of Chemistry, is the study of the interactions between Atoms, small Molecules, and light (or Electromagnetic radiation Similarly, electrons can be ejected from a metal plate by shining light of sufficiently high frequency on it (the photoelectric effect); the energy of the ejected electron is related only to the light's frequency, not to its intensity. Introduction When a Metallic surface is exposed to Electromagnetic radiation above a certain threshold Frequency, the light is absorbed and Electrons
At the same time, investigations of blackbody radiation carried out over four decades (1860–1900) by various researchers[24] culminated in Max Planck's hypothesis[25][26] that the energy of any system that absorbs or emits electromagnetic radiation of frequency ν is an integer multiple of an energy quantum E = hν. The Electromagnetic radiation emitted by a Black body. You may also be looking for Incandescence, the radiation from a body The Planck constant (denoted h\ is a Physical constant used to describe the sizes of quanta. As shown by Albert Einstein,[5][6] some form of energy quantization must be assumed to account for the thermal equilibrium observed between matter and electromagnetic radiation; for this explanation of the photoelectric effect, Einstein received the 1921 Nobel Prize in physics. Albert Einstein ( German: ˈalbɐt ˈaɪ̯nʃtaɪ̯n; English: ˈælbɝt ˈaɪnstaɪn (14 March 1879 – 18 April 1955 was a German -born theoretical Electromagnetic radiation takes the form of self-propagating Waves in a Vacuum or in Matter. Introduction When a Metallic surface is exposed to Electromagnetic radiation above a certain threshold Frequency, the light is absorbed and Electrons The Nobel Prize (Nobelpriset (Nobelprisen is a Swedish prize established in the 1895 will of Swedish chemist Alfred Nobel; it was first awarded in Peace, Literature
Since the Maxwell theory of light allows for all possible energies of electromagnetic radiation, most physicists assumed initially that the energy quantization resulted from some unknown constraint on the matter that absorbs or emits the radiation. In 1905, Einstein was the first to propose that energy quantization was a property of electromagnetic radiation itself. [5] Although he accepted the validity of Maxwell's theory, Einstein pointed out that many anomalous experiments could be explained if the energy of a Maxwellian light wave were localized into point-like quanta that move independently of one another, even if the wave itself is spread continuously over space. [5] In 1909[6] and 1916,[8] Einstein showed that, if Planck's law of black-body radiation is accepted, the energy quanta must also carry momentum p = h / λ, making them full-fledged particles. For a general introduction see Black body. In Physics, Planck's law describes the spectral radiance of Electromagnetic radiation In Classical mechanics, momentum ( pl momenta SI unit kg · m/s, or equivalently N · s) is the product In Particle physics, an elementary particle or fundamental particle is a particle not known to have substructure that is it is not known to be made This photon momentum was observed experimentally[27] by Arthur Compton, for which he received the Nobel Prize in 1927. Arthur Holly Compton (September 10 1892 &ndash March 15 1962 was an American physicist and Nobel laureate in physics for his discovery of the Compton effect The Nobel Prize (Nobelpriset (Nobelprisen is a Swedish prize established in the 1895 will of Swedish chemist Alfred Nobel; it was first awarded in Peace, Literature The pivotal question was then: how to unify Maxwell's wave theory of light with its experimentally observed particle nature? The answer to this question occupied Albert Einstein for the rest of his life,[28] and was solved in quantum electrodynamics and its successor, the Standard Model. Albert Einstein ( German: ˈalbɐt ˈaɪ̯nʃtaɪ̯n; English: ˈælbɝt ˈaɪnstaɪn (14 March 1879 – 18 April 1955 was a German -born theoretical Quantum electrodynamics ( QED) is a relativistic Quantum field theory of Electrodynamics. The Standard Model of Particle physics is a theory that describes three of the four known Fundamental interactions together with the Elementary particles
Early objections
Einstein's 1905 predictions were verified experimentally in several ways within the first two decades of the 20th century, as recounted in Robert Millikan's Nobel lecture. Robert Andrews Millikan (March 22 1868 – December 19 1953 was an American experimental physicist, and Nobel laureate in physics for his measurement [29] However, before Compton's experiment[27] showing that photons carried momentum proportional to their frequency (1922), most physicists were reluctant to believe that electromagnetic radiation itself might be particulate. The Compton shift formula Klein-Nishina formulaCompton used a combination of three fundamental formulas representing the various aspects of classical and modern physics combining In Classical mechanics, momentum ( pl momenta SI unit kg · m/s, or equivalently N · s) is the product Frequency is a measure of the number of occurrences of a repeating event per unit Time. Electromagnetic radiation takes the form of self-propagating Waves in a Vacuum or in Matter. (See, for example, the Nobel lectures of Wien,[24] Planck[26] and Millikan. Wilhelm Carl Werner Otto Fritz Franz Wien ( German:) ( 13 January 1864 &ndash 30 August 1928) was a German physicist [29]) This reluctance is understandable, given the success and plausibility of Maxwell's electromagnetic wave model of light. Therefore, most physicists assumed rather that energy quantization resulted from some unknown constraint on the matter that absorbs or emits radiation. Niels Bohr, Arnold Sommerfeld and others developed atomic models with discrete energy levels that could account qualitatively for the sharp spectral lines and energy quantization observed in the emission and absorption of light by atoms; their models agreed excellently with the spectrum of hydrogen, but not with those of other atoms. Niels Henrik David Bohr (nels ˈb̥oɐ̯ˀ in Danish 7 October 1885 – 18 November 1962 was a Danish Physicist who made fundamental contributions to understanding Arnold Johannes Wilhelm Sommerfeld (5 December 1868 &ndash 26 April 1951 was a German theoretical Physicist who pioneered developments in atomic In Physics, emission is the process by which the Energy of a Photon is released by another entity for example by an Atom whose Electrons In Physics, absorption of electromagnetic radiation is the process by which the Energy of a Photon is taken up by matter typically the electrons of an It was only the Compton scattering of a photon by a free electron (which can have no energy levels, since it has no internal structure) that convinced most physicists that light itself was quantized.
Even after Compton's experiment, Bohr, Hendrik Kramers and John Slater made one last attempt to preserve the Maxwellian continuous electromagnetic field model of light, the so-called BKS model. Hendrik Anthony Kramers ( Rotterdam, February 2, 1894 &ndash Oegstgeest, April 24, 1952) was a Dutch Physicist John Clarke Slater (1900-1976 was a noted American physicist and theoretical chemist. [30] To account for the then-available data, two drastic hypotheses had to be made:
- Energy and momentum are conserved only on the average in interactions between matter and radiation, not in elementary processes such as absorption and emission. This allows one to reconcile the discontinuously changing energy of the atom (jump between energy states) with the continuous release of energy into radiation.
- Causality is abandoned. For example, spontaneous emissions are merely emissions induced by a "virtual" electromagnetic field. Spontaneous emission is the process by which a light source such as an Atom, Molecule, Nanocrystal or nucleus in an Excited state In Optics, stimulated emission is the process by which an electron perturbed by a Photon having the correct energy may drop to a lower Energy level resulting
However, refined Compton experiments showed that energy-momentum is conserved extraordinarily well in elementary processes; and also that the jolting of the electron and the generation of a new photon in Compton scattering obey causality to within 10 ps. The Compton shift formula Klein-Nishina formulaCompton used a combination of three fundamental formulas representing the various aspects of classical and modern physics combining To help compare Orders of magnitude of different Times this page lists times between 10&minus12 seconds and 10&minus11 seconds (1 Pico Accordingly, Bohr and his co-workers gave their model “as honorable a funeral as possible“. [28] Nevertheless, the BKS model inspired Werner Heisenberg in his development[31] of quantum mechanics. Werner Heisenberg (5 December 1901 in Würzburg &ndash1 February 1976 in Munich) was a German theoretical physicist best known for enunciating the Quantum mechanics is the study of mechanical systems whose dimensions are close to the Atomic scale such as Molecules Atoms Electrons
A few physicists persisted[32] in developing semiclassical models in which electromagnetic radiation is not quantized, but matter obeys the laws of quantum mechanics. Electromagnetic radiation takes the form of self-propagating Waves in a Vacuum or in Matter. Quantum mechanics is the study of mechanical systems whose dimensions are close to the Atomic scale such as Molecules Atoms Electrons Although the evidence for photons from chemical and physical experiments was overwhelming by the 1970s, this evidence could not be considered as absolutely definitive; since it relied on the interaction of light with matter, a sufficiently complicated theory of matter could in principle account for the evidence. Nevertheless, all semiclassical theories were refuted definitively in the 1970s and 1980s by elegant photon-correlation experiments. [33] Hence, Einstein's hypothesis that quantization is a property of light itself is considered to be proven.
Wave–particle duality and uncertainty principles
- See also: Wave–particle duality, Squeezed coherent state, and Uncertainty principle
Photons, like all quantum objects, exhibit both wave-like and particle-like properties. In Physics and Chemistry, wave–particle duality is the concept that all Matter and Energy exhibits both Wave -like and In Physics, a squeezed coherent state is any state of the Quantum mechanical Hilbert space such that the Uncertainty principle is saturated In Quantum physics, the Heisenberg uncertainty principle states that locating a particle in a small region of space makes the Momentum of the particle uncertain Their dual wave–particle nature can be difficult to visualize. The photon displays clearly wave-like phenomena such as diffraction and interference on the length scale of its wavelength. Diffraction is normally taken to refer to various phenomena which occur when a wave encounters an obstacle In physics interference is the addition ( superposition) of two or more Waves that result in a new wave pattern For example, a single photon passing through a double-slit experiment lands on the screen with a probability distribution given by its interference pattern determined by Maxwell's equations. In Probability theory and Statistics, a probability distribution identifies either the probability of each value of an unidentified Random variable In Classical electromagnetism, Maxwell's equations are a set of four Partial differential equations that describe the properties of the electric [34] However, experiments confirm that the photon is not a short pulse of electromagnetic radiation; it does not spread out as it propagates, nor does it divide when it encounters a beam splitter. A beam splitter is an optical device that splits a beam of Light in two Rather, the photon seems like a point-like particle, since it is absorbed or emitted as a whole by arbitrarily small systems, systems much smaller than its wavelength, such as an atomic nucleus (≈10–15 m across) or even the point-like electron. A point particle (or point-like, often spelled pointlike) is an idealized object heavily used in Physics. The electron is a fundamental Subatomic particle that was identified and assigned the negative charge in 1897 by J Nevertheless, the photon is not a point-like particle whose trajectory is shaped probabilistically by the electromagnetic field, as conceived by Einstein and others; that hypothesis was also refuted by the photon-correlation experiments cited above. The electromagnetic field is a physical field produced by electrically charged objects. Albert Einstein ( German: ˈalbɐt ˈaɪ̯nʃtaɪ̯n; English: ˈælbɝt ˈaɪnstaɪn (14 March 1879 – 18 April 1955 was a German -born theoretical [33] According to our present understanding, the electromagnetic field itself is produced by photons, which in turn result from a local gauge symmetry and the laws of quantum field theory (see the Second quantization and Gauge boson sections below). Gauge theory is a peculiar Quantum field theory where the Lagrangian is invariant under certain transformations In quantum field theory (QFT the forces between particles are mediated by other particles In Physics, the photon is the Elementary particle responsible for electromagnetic phenomena In Physics, the photon is the Elementary particle responsible for electromagnetic phenomena
A key element of quantum mechanics is Heisenberg's uncertainty principle, which forbids the simultaneous measurement of the position and momentum of a particle along the same direction. Quantum mechanics is the study of mechanical systems whose dimensions are close to the Atomic scale such as Molecules Atoms Electrons Werner Heisenberg (5 December 1901 in Würzburg &ndash1 February 1976 in Munich) was a German theoretical physicist best known for enunciating the In Quantum physics, the Heisenberg uncertainty principle states that locating a particle in a small region of space makes the Momentum of the particle uncertain Remarkably, the uncertainty principle for charged, material particles requires the quantization of light into photons, and even the frequency dependence of the photon's energy and momentum. An elegant illustration is Heisenberg's thought experiment for locating an electron with an ideal microscope. A thought experiment (from the German Gedankenexperiment) is a proposal for an Experiment that would test a Hypothesis or Theory [35] The position of the electron can be determined to within the resolving power of the microscope, which is given by a formula from classical optics
where θ is the aperture angle of the microscope. Angular resolution describes the resolving power of any image forming device such as an optical or Radio telescope, a Microscope, a Camera The angular aperture of a lens is the apparent Angle of the lens Aperture as seen from the focal point: a = 2 \arctan Thus, the position uncertainty Δx can be made arbitrarily small by reducing the wavelength. The momentum of the electron is uncertain, since it received a “kick” Δp from the light scattering from it into the microscope. If light were not quantized into photons, the uncertainty Δp could be made arbitrarily small by reducing the light's intensity. In that case, since the wavelength and intensity of light can be varied independently, one could simultaneously determine the position and momentum to arbitrarily high accuracy, violating the uncertainty principle. In Quantum physics, the Heisenberg uncertainty principle states that locating a particle in a small region of space makes the Momentum of the particle uncertain By contrast, Einstein's formula for photon momentum preserves the uncertainty principle; since the photon is scattered anywhere within the aperture, the uncertainty of momentum transferred equals
giving the product 
, which is Heisenberg's uncertainty principle. Thus, the entire world is quantized; both matter and fields must obey a consistent set of quantum laws, if either one is to be quantized.
The analogous uncertainty principle for photons forbids the simultaneous measurement of the number n of photons (see Fock state and the Second quantization section below) in an electromagnetic wave and the phase φ of that wave
- ΔnΔφ > 1
See coherent state and squeezed coherent state for more details. A Fock state, in Quantum mechanics, is any state of the Fock space with a well-defined number of particles in each state In Physics, the photon is the Elementary particle responsible for electromagnetic phenomena In Quantum mechanics a coherent state is a specific kind of quantum state of the Quantum harmonic oscillator whose dynamics most closely resemble the oscillating behaviour In Physics, a squeezed coherent state is any state of the Quantum mechanical Hilbert space such that the Uncertainty principle is saturated
Both photons and material particles such as electrons create analogous interference patterns when passing through a double-slit experiment. In physics interference is the addition ( superposition) of two or more Waves that result in a new wave pattern For photons, this corresponds to the interference of a Maxwell light wave whereas, for material particles, this corresponds to the interference of the Schrödinger wave equation. The electromagnetic wave equation is a second-order partial differential equation that describes the propagation of Electromagnetic waves through a medium In Physics, especially Quantum mechanics, the Schrödinger equation is an equation that describes how the Quantum state of a Physical system Although this similarity might suggest that Maxwell's equations are simply Schrödinger's equation for photons, most physicists do not agree. In Classical electromagnetism, Maxwell's equations are a set of four Partial differential equations that describe the properties of the electric [36][37] For one thing, they are mathematically different; most obviously, Schrödinger's one equation solves for a complex field, whereas Maxwell's four equations solve for real fields. Complex plane In Mathematics, the complex numbers are an extension of the Real numbers obtained by adjoining an Imaginary unit, denoted In Physics, a field is a Physical quantity associated to each point of Spacetime. In Mathematics, the real numbers may be described informally in several different ways In Physics, a field is a Physical quantity associated to each point of Spacetime. More generally, the normal concept of a Schrödinger probability wave function cannot be applied to photons. In Quantum mechanics, a probability amplitude is a complex -valued function that describes an uncertain or unknown quantity A wave function or wavefunction is a mathematical tool used in Quantum mechanics to describe any physical system [38] Being massless, they cannot be localized without being destroyed; technically, photons cannot have a position eigenstate 
, and, thus, the normal Heisenberg uncertainty principle ΔxΔp > h / 2 does not pertain to photons. A few substitute wave functions have been suggested for the photon,[39][40][41][42] but they have not come into general use. Instead, physicists generally accept the second-quantized theory of photons described below, quantum electrodynamics, in which photons are quantized excitations of electromagnetic modes. Quantum electrodynamics ( QED) is a relativistic Quantum field theory of Electrodynamics.
Bose–Einstein model of a photon gas
In 1924, Satyendra Nath Bose derived Planck's law of black-body radiation without using any electromagnetism, but rather a modification of coarse-grained counting of phase space. An ideal Bose gas is a quantum-mechanical version of a classical Ideal gas. In Statistical mechanics, Bose - Einstein statistics (or more colloquially B-E statistics determines the statistical distribution of The spin-statistics theorem in Quantum mechanics relates the spin of a particle to the statistics obeyed by that particle Satyendra Nath Bose (/sɐθjinðrɐ nɑθ bos/ সত্যেন্দ্র নাথ বসু ( January 1, 1894 &ndash February 4, 1974 For a general introduction see Black body. In Physics, Planck's law describes the spectral radiance of Electromagnetic radiation In Mathematics and Physics, a phase space, introduced by Willard Gibbs in 1901 is a Space in which all possible states of a System [43] Einstein showed that this modification is equivalent to assuming that photons are rigorously identical and that it implied a “mysterious non-local interaction”,[44][45] now understood as the requirement for a symmetric quantum mechanical state. Identical particles, or indistinguishable particles, are particles that cannot be distinguished from one another even in principle This work led to the concept of coherent states and the development of the laser. In Quantum mechanics a coherent state is a specific kind of quantum state of the Quantum harmonic oscillator whose dynamics most closely resemble the oscillating behaviour In the same papers, Einstein extended Bose's formalism to material particles (bosons) and predicted that they would condense into their lowest quantum state at low enough temperatures; this Bose–Einstein condensation was observed experimentally in 1995. In Particle physics, bosons are particles which obey Bose-Einstein statistics; they are named after Satyendra Nath Bose and Albert Einstein A Bose–Einstein condensate (BEC is a State of matter of Bosons confined in an external Potential and cooled to Temperatures very near to [46]
Photons must obey Bose–Einstein statistics if they are to allow the superposition principle of electromagnetic fields, the condition that Maxwell's equations are linear. In Statistical mechanics, Bose - Einstein statistics (or more colloquially B-E statistics determines the statistical distribution of In Physics and Systems theory, the superposition principle, also known as superposition property, states that for all Linear systems The electromagnetic field is a physical field produced by electrically charged objects. In Classical electromagnetism, Maxwell's equations are a set of four Partial differential equations that describe the properties of the electric All particles are divided into bosons and fermions, depending on whether they have integer or half-integer spin, respectively. In Particle physics, bosons are particles which obey Bose-Einstein statistics; they are named after Satyendra Nath Bose and Albert Einstein In Particle physics, fermions are particles which obey Fermi-Dirac statistics; they are named after Enrico Fermi. In Quantum mechanics, spin is a fundamental property of atomic nuclei, Hadrons and Elementary particles For particles with non-zero spin The spin-statistics theorem shows that all bosons obey Bose–Einstein statistics, whereas all fermions obey Fermi-Dirac statistics or, equivalently, the Pauli exclusion principle, which states that at most one particle can occupy any given state. The spin-statistics theorem in Quantum mechanics relates the spin of a particle to the statistics obeyed by that particle In Statistical mechanics, Fermi-Dirac statistics is a particular case of Particle statistics developed by Enrico Fermi and Paul Dirac that The Pauli exclusion principle is a quantum mechanical principle formulated by Wolfgang Pauli in 1925 Thus, if the photon were a fermion, only one photon could move in a particular direction at a time. This is inconsistent with the experimental observation that lasers can produce coherent light of arbitrary intensity, that is, with many photons moving in the same direction. Hence, the photon must be a boson and obey Bose–Einstein statistics.
Stimulated and spontaneous emission
In 1916, Einstein showed that Planck's quantum hypothesis E = hν could be derived from a kinetic rate equation. [7] Consider a cavity in thermal equilibrium and filled with electromagnetic radiation and systems that can emit and absorb that radiation. In Thermodynamics, a thermodynamic system is said to be in thermodynamic equilibrium when it is in thermal equilibrium Mechanical equilibrium, and Electromagnetic radiation takes the form of self-propagating Waves in a Vacuum or in Matter. Thermal equilibrium requires that the number density ρ(ν) of photons with frequency ν is constant in time; hence, the rate of emitting photons of that frequency must equal the rate of absorbing them.
Einstein hypothesized that the rate Rji for a system to absorb a photon of frequency ν and transition from a lower energy Ej to a higher energy Ei was proportional to the number Nj of molecules with energy Ej and to the number density ρ(ν) of ambient photons with that frequency
where Bji is the rate constant for absorption. In Chemical kinetics a reaction rate constant k or \lambda quantifies the speed of a Chemical reaction.
More daringly, Einstein hypothesized that the reverse rate Rij for a system to emit a photon of frequency ν and transition from a higher energy Ei to a lower energy Ej was composed of two terms:
where Aij is the rate constant for emitting a photon spontaneously, and Bij is the rate constant for emitting it in response to ambient photons (induced or stimulated emission). Spontaneous emission is the process by which a light source such as an Atom, Molecule, Nanocrystal or nucleus in an Excited state In Optics, stimulated emission is the process by which an electron perturbed by a Photon having the correct energy may drop to a lower Energy level resulting Einstein showed that Planck's energy formula E = hν is a necessary consequence of these hypothesized rate equations and the basic requirements that the ambient radiation be in thermal equilibrium with the systems that absorb and emit the radiation and independent of the systems' material composition.
This simple kinetic model was a powerful stimulus for research. Einstein was able to show that Bij = Bji (i. e. , the rate constants for induced emission and absorption are equal) and, perhaps more remarkably,
Einstein did not attempt to justify his rate equations but noted that Aij and Bij should be derivable from a “mechanics and electrodynamics modified to accommodate the quantum hypothesis”. This prediction was borne out in quantum mechanics and quantum electrodynamics, respectively; both are required to derive Einstein's rate constants from first principles. Quantum mechanics is the study of mechanical systems whose dimensions are close to the Atomic scale such as Molecules Atoms Electrons Quantum electrodynamics ( QED) is a relativistic Quantum field theory of Electrodynamics. Paul Dirac derived the Bij rate constants in 1926 using a semiclassical approach,[47] and, in 1927, succeeded in deriving all the rate constants from first principles. [48][49] Dirac's work was the foundation of quantum electrodynamics, i. e. , the quantization of the electromagnetic field itself. Dirac's approach is also called second quantization or quantum field theory;[50][51][52] the earlier quantum mechanics (the quantization of material particles moving in a potential) represents the “first quantization”. In quantum field theory (QFT the forces between particles are mediated by other particles
Einstein was troubled by the fact that his theory seemed incomplete, since it did not determine the direction of a spontaneously emitted photon. A probabilistic nature of light-particle motion was first considered by Newton in his treatment of birefringence and, more generally, of the splitting of light beams at interfaces into a transmitted beam and a reflected beam. Sir Isaac Newton, FRS (ˈnjuːtən 4 January 1643 31 March 1727) Biography Early years See also Isaac Newton's early life and achievements Birefringence, or double refraction, is the decomposition of a ray of Light into two rays (the ordinary ray and the extraordinary ray Newton hypothesized that hidden variables in the light particle determined which path it would follow. [20] Similarly, Einstein hoped for a more complete theory that would leave nothing to chance, beginning his separation[28] from quantum mechanics. Ironically, Max Born's probabilistic interpretation of the wave function[53][54] was inspired by Einstein's later work searching for a more complete theory. Max Born (11 December 1882 &ndash 5 January 1970 was a German Physicist and Mathematician who was instrumental in the development of Quantum In Quantum mechanics, a probability amplitude is a complex -valued function that describes an uncertain or unknown quantity A wave function or wavefunction is a mathematical tool used in Quantum mechanics to describe any physical system [55]
Second quantization
In 1910, Peter Debye derived Planck's law of black-body radiation from a relatively simple assumption. Peter Joseph William Debye ( March 24 1884 &ndash November 2 1966) was a Dutch physicist and physical chemist For a general introduction see Black body. In Physics, Planck's law describes the spectral radiance of Electromagnetic radiation [56] He correctly decomposed the electromagnetic field in a cavity into its Fourier modes, and assumed that the energy in any mode was an integer multiple of hν, where ν is the frequency of the electromagnetic mode. In Mathematics, a Fourier series decomposes a periodic function into a sum of simple oscillating functions Planck's law of black-body radiation follows immediately as a geometric sum. However, Debye's approach failed to give the correct formula for the energy fluctuations of blackbody radiation, which were derived by Einstein in 1909. [6]
In 1925, Born, Heisenberg and Jordan reinterpreted Debye's concept in a key way. Max Born (11 December 1882 &ndash 5 January 1970 was a German Physicist and Mathematician who was instrumental in the development of Quantum Werner Heisenberg (5 December 1901 in Würzburg &ndash1 February 1976 in Munich) was a German theoretical physicist best known for enunciating the Pascual Jordan (b October 18, 1902 in Hanover, Germany; d July 31, 1980 in Hamburg, Federal Republic [57] As may be shown classically, the Fourier modes of the electromagnetic field—a complete set of electromagnetic plane waves indexed by their wave vector k and polarization state—are equivalent to a set of uncoupled simple harmonic oscillators. In Mathematics, a Fourier series decomposes a periodic function into a sum of simple oscillating functions The electromagnetic four-potential is a covariant Four-vector defined in volt·seconds/meter (and in maxwell/centimeter in parentheses Treated quantum mechanically, the energy levels of such oscillators are known to be E = nhν, where ν is the oscillator frequency. The key new step was to identify an electromagnetic mode with energy E = nhν as a state with n photons, each of energy hν. This approach gives the correct energy fluctuation formula.
Dirac took this one step further. [48][49] He treated the interaction between a charge and an electromagnetic field as a small perturbation that induces transitions in the photon states, changing the numbers of photons in the modes, while conserving energy and momentum overall. Dirac was able to derive Einstein's Aij and Bij coefficients from first principles, and showed that the Bose–Einstein statistics of photons is a natural consequence of quantizing the electromagnetic field correctly (Bose's reasoning went in the opposite direction; he derived Planck's law of black body radiation by assuming BE statistics). For a general introduction see Black body. In Physics, Planck's law describes the spectral radiance of Electromagnetic radiation In Dirac's time, it was not yet known that all bosons, including photons, must obey BE statistics.
Dirac's second-order perturbation theory can involve virtual photons, transient intermediate states of the electromagnetic field; the static electric and magnetic interactions are mediated by such virtual photons. In Quantum mechanics, perturbation theory is a set of approximation schemes directly related to mathematical perturbation for describing a complicated quantum system In Physics, a virtual particle is a particle that exists for a limited time and space introducing uncertainty in their energy and momentum due to the Heisenberg Uncertainty ---- Bold text Coulomb's law', developed in the 1780s by French physicist Charles Augustin de Coulomb, may be stated in scalar form In Physics, magnetism is one of the Phenomena by which Materials exert attractive or repulsive Forces on other Materials. In such quantum field theories, the probability amplitude of observable events is calculated by summing over all possible intermediate steps, even ones that are unphysical; hence, virtual photons are not constrained to satisfy E = pc, and may have extra polarization states; depending on the gauge used, virtual photons may have three or four polarization states, instead of the two states of real photons. In quantum field theory (QFT the forces between particles are mediated by other particles In Quantum mechanics, a probability amplitude is a complex -valued function that describes an uncertain or unknown quantity Polarization ( ''Brit'' polarisation) is a property of Waves that describes the orientation of their oscillations In the Physics of gauge theories, gauge fixing (also called choosing a gauge) denotes a mathematical procedure for coping with redundant degrees Although these transient virtual photons can never be observed, they contribute measurably to the probabilities of observable events. Indeed, such second-order and higher-order perturbation calculations can give apparently infinite contributions to the sum. Infinity (symbolically represented with ∞) comes from the Latin infinitas or "unboundedness Such unphysical results are corrected for using the technique of renormalization. In Quantum field theory, the Statistical mechanics of fields and the theory of self-similar geometric structures renormalization refers to a collection Other virtual particles may contribute to the summation as well; for example, two photons may interact indirectly through virtual electron-positron pairs. The electron is a fundamental Subatomic particle that was identified and assigned the negative charge in 1897 by J The positrons or antielectron is the Antiparticle or the Antimatter counterpart of the Electron. See also Electron-positron annihilation Meitner–Hupfeld effect Pair instability supernova
In modern physics notation, the quantum state of the electromagnetic field is written as a Fock state, a tensor product of the states for each electromagnetic mode
where 
represents the state in which 
photons are in the mode ki. In Quantum physics, a quantum state is a mathematical object that fully describes a quantum system. A Fock state, in Quantum mechanics, is any state of the Fock space with a well-defined number of particles in each state In Mathematics, the tensor product, denoted by \otimes may be applied in different contexts to vectors matrices, Tensors Vector In this notation, the creation of a new photon in mode ki (e. g. , emitted from an atomic transition) is written as 
. This notation merely expresses the concept of Born, Heisenberg and Jordan described above, and does not add any physics.
The photon as a gauge boson
The electromagnetic field can be understood as a gauge theory, i. Gauge theory is a peculiar Quantum field theory where the Lagrangian is invariant under certain transformations Gauge theory is a peculiar Quantum field theory where the Lagrangian is invariant under certain transformations e. , as a field that results from requiring that symmetry hold independently at every position in spacetime. SpaceTime is a patent-pending three dimensional graphical user interface that allows end users to search their content such as Google Google Images Yahoo! YouTube eBay Amazon and RSS [58] For the electromagnetic field, this gauge symmetry is the Abelian U(1) symmetry of a complex number, which reflects the ability to vary the phase of a complex number without affecting real numbers made from it, such as the energy or the Lagrangian. The electromagnetic field is a physical field produced by electrically charged objects. An abelian group, also called a commutative group, is a group satisfying the additional requirement that the product of elements does not depend on their order (the In Mathematics, the unitary group of degree n, denoted U( n) is the group of n × n unitary matrices Complex plane In Mathematics, the complex numbers are an extension of the Real numbers obtained by adjoining an Imaginary unit, denoted In Mathematics, complex geometry is the studyof Complex manifolds and functions of many complex variables In Mathematics, the real numbers may be described informally in several different ways In Physics and other Sciences energy (from the Greek grc ἐνέργεια - Energeia, "activity operation" from grc ἐνεργός The Lagrangian, L of a Dynamical system is a function that summarizes the dynamics of the system
The quanta of an Abelian gauge field must be massless, uncharged bosons, as long as the symmetry is not broken; hence, the photon is predicted to be massless, and to have zero electric charge and integer spin. Gauge theory is a peculiar Quantum field theory where the Lagrangian is invariant under certain transformations Electric charge is a fundamental conserved property of some Subatomic particles which determines their Electromagnetic interaction. The particular form of the electromagnetic interaction specifies that the photon must have spin ±1; thus, its helicity must be . In Physics, the electromagnetic force is the force that the Electromagnetic field exerts on electrically charged particles In Quantum mechanics, spin is a fundamental property of atomic nuclei, Hadrons and Elementary particles For particles with non-zero spin In Particle physics, helicity is the projection of the spin \vec S onto the direction of momentum \hat p: h = \vec These two spin components correspond to the classical concepts of right-handed and left-handed circularly polarized light. In Electrodynamics, circular polarization (also circular polarisation) of Electromagnetic radiation is a Polarization such that the tip of the However, the transient virtual photons of quantum electrodynamics may also adopt unphysical polarization states. In Physics, a virtual particle is a particle that exists for a limited time and space introducing uncertainty in their energy and momentum due to the Heisenberg Uncertainty Quantum electrodynamics ( QED) is a relativistic Quantum field theory of Electrodynamics. [58]
In the prevailing Standard Model of physics, the photon is one of four gauge bosons in the electroweak interaction; the other three are denoted W+, W− and Z0 and are responsible for the weak interaction. The Standard Model of Particle physics is a theory that describes three of the four known Fundamental interactions together with the Elementary particles In Particle physics, gauge bosons are Bosonic particles that act as carriers of the fundamental forces of nature In Particle physics, the electroweak interaction is the unified description of two of the four Fundamental interactions of nature Electromagnetism and the The W and Z bosons are the Elementary particles that mediate the Weak force. The weak interaction (often called the weak force or sometimes the weak nuclear force) is one of the four Fundamental interactions of nature Unlike the photon, these gauge bosons have invariant mass, owing to a mechanism that breaks their SU(2) gauge symmetry. The Higgs mechanism is Spontaneous symmetry breaking in a Gauge theory. Special Unit 2In Mathematics, the special unitary group of degree n, denoted SU( n) is the group of n × n The unification of the photon with W and Z gauge bosons in the electroweak interaction was accomplished by Sheldon Glashow, Abdus Salam and Steven Weinberg, for which they were awarded the 1979 Nobel Prize in physics. Sheldon Lee Glashow (born December 5, 1932) is an American physicist. Abdus Salam ( Urdu: محمد عبد السلام) ( January 29, 1926; Jhang Punjab &ndash November 21, Steven Weinberg (born May 3, 1933) is an American Physicist, and Nobel laureate in Physics for his contributions with Abdus Salam The Nobel Prize (Nobelpriset (Nobelprisen is a Swedish prize established in the 1895 will of Swedish chemist Alfred Nobel; it was first awarded in Peace, Literature [59][60][61] Physicists continue to hypothesize grand unified theories that connect these four gauge bosons with the eight gluon gauge bosons of quantum chromodynamics; however, key predictions of these theories, such as proton decay, have not been observed experimentally. Grand Unification, grand unified theory, or GUT refers to any of several very similar unified field theories or models in Physics that In Particle physics, gauge bosons are Bosonic particles that act as carriers of the fundamental forces of nature Gluons ( Glue and the suffix -on) are Elementary particles that cause Quarks to interact and are indirectly responsible for the Quantum chromodynamics (abbreviated as QCD is a theory of the Strong interaction ( color force a Fundamental force describing the interactions of the In Particle physics, proton decay is a hypothetical form of Radioactive decay in which the Proton decays into lighter Subatomic particles
Photon structure
According to Quantum Chromodynamics, a real photon can interact both as a point-like particle, or as a collection of quarks and gluons, i. Quantum chromodynamics (abbreviated as QCD is a theory of the Strong interaction ( color force a Fundamental force describing the interactions of the Quantum chromodynamics (abbreviated as QCD is a theory of the Strong interaction ( color force a Fundamental force describing the interactions of the In Physics, a quark (kwɔrk kwɑːk or kwɑːrk is a type of Subatomic particle. Gluons ( Glue and the suffix -on) are Elementary particles that cause Quarks to interact and are indirectly responsible for the e. , like a hadron. In Particle physics, a hadron ( from the ἁδρός hadrós, " stout, thick " ( The structure of the photon is determined not by the traditional valence quark distributions as in a proton, but by fluctuations of the point-like photon into a collection of partons. The proton ( Greek πρῶτον / proton "first" is a Subatomic particle with an Electric charge of one positive In Particle physics, the parton model was proposed by Richard Feynman in 1969 as a way to analyze high-energy Hadron collisions [62]
Contributions to the mass of a system
- See also: Mass in special relativity and Gravitation
The energy of a system that emits a photon is decreased by the energy E of the photon as measured in the rest frame of the emitting system, which may result in a reduction in mass in the amount E / c2. The term Mass in Special relativity usually refers to the Rest mass of the object which is the Newtonian mass as measured by an observer moving along with Gravitation is a natural Phenomenon by which objects with Mass attract one another Similarly, the mass of a system that absorbs a photon is increased by a corresponding amount.
This concept is applied in a key prediction of QED, the theory of quantum electrodynamics begun by Dirac (described above). Quantum electrodynamics ( QED) is a relativistic Quantum field theory of Electrodynamics. QED is able to predict the magnetic dipole moment of leptons to extremely high accuracy; experimental measurements of these magnetic dipole moments have agreed with these predictions perfectly. In Quantum electrodynamics, the anomalous magnetic moment of a particle is a contribution of effects of Quantum mechanics, expressed by Feynman diagrams Leptons are a family of fundamental Subatomic particles comprising the Electron, the Muon, and the Tauon (or tau particle as well as their The predictions, however, require counting the contributions of virtual photons to the mass of the lepton. Another example of such contributions verified experimentally is the QED prediction of the Lamb shift observed in the hyperfine structure of bound lepton pairs, such as muonium and positronium. In Physics, the Lamb shift, named after Willis Lamb (1913-2008 is a small difference in Energy between two Energy levels ^2S_{1/2} In Atomic physics, hyperfine coupling is the weak magnetic interaction between Electrons and nuclei. Muonium particles are Exotic atoms made up of an Antimuon and an Electron, and are given the chemical symbol. Positronium ( Ps) is a system consisting of an Electron and its anti-particle, a Positron, bound together into an " Exotic atom
Since photons contribute to the stress-energy tensor, they exert a gravitational attraction on other objects, according to the theory of general relativity. The stress-energy tensor (sometimes stress-energy-momentum tensor is a Tensor quantity in Physics that describes the Density and Flux Gravitation is a natural Phenomenon by which objects with Mass attract one another General relativity or the general theory of relativity is the geometric theory of Gravitation published by Albert Einstein in 1916 Conversely, photons are themselves affected by gravity; their normally straight trajectories may be bent by warped spacetime, as in gravitational lensing, and their frequencies may be lowered by moving to a higher gravitational potential, as in the Pound-Rebka experiment. SpaceTime is a patent-pending three dimensional graphical user interface that allows end users to search their content such as Google Google Images Yahoo! YouTube eBay Amazon and RSS A gravitational lens is formed when the light from a very distant bright source (such as a Quasar) is "bent" around a massive object (such as a cluster of In Physics, Light or other forms of Electromagnetic radiation of a certain wavelength originating from a source placed in a region of stronger gravitational Potential energy can be thought of as Energy stored within a physical system The Pound-Rebka experiment is a well known experiment to test Albert Einstein 's theory of General relativity. However, these effects are not specific to photons; exactly the same effects would be predicted for classical electromagnetic waves. Electromagnetic radiation takes the form of self-propagating Waves in a Vacuum or in Matter.
Photons in matter
- See also: Group velocity and Photochemistry
Light that travels through transparent matter does so at a lower speed than c, the speed of light in a vacuum. The group velocity of a Wave is the Velocity with which the variations in the shape of the wave's amplitude (known as the modulation or envelope Photochemistry, a sub-discipline of Chemistry, is the study of the interactions between Atoms, small Molecules, and light (or Electromagnetic radiation For example, photons suffer so many collisions on the way from the core of the sun that radiant energy can take about a million years to reach the surface;[63] however, once in open space, a photon takes only 8. 3 minutes to reach Earth. The factor by which the speed is decreased is called the refractive index of the material. The refractive index (or index of Refraction) of a medium is a measure for how much the speed of light (or other waves such as sound waves is reduced inside the medium In a classical wave picture, the slowing can be explained by the light inducing electric polarization in the matter, the polarized matter radiating new light, and the new light interfering with the original light wave to form a delayed wave. In a particle picture, the slowing can instead be described as a blending of the photon with quantum excitations of the matter (quasi-particles such as phonons and excitons) to form a polariton; this polariton has a nonzero effective mass, which means that it cannot travel at c. In Physics, a quasiparticle refers to a particle -like entity arising in certain systems of interacting particles In Physics, a phonon is a quantized mode of vibration occurring in a rigid crystal lattice, such as the Atomic lattice of a Solid This page is about the Quasiparticle. Exciton is also the title of a single by IDM composer Squarepusher. In Physics, polaritons are Quasiparticles resulting from strong coupling of Electromagnetic waves with an electric or magnetic Dipole -carrying In Solid state physics, a particle's effective mass is the Mass it seems to carry in the semiclassical model of transport in a Crystal. Light of different frequencies may travel through matter at different speeds; this is called dispersion. The variable speed of light (VSL concept states that the Speed of light in a vacuum usually denoted by c, may not be Constant in some cases In Optics, dispersion is the phenomenon in which the Phase velocity of a wave depends on its frequency The polariton propagation speed v equals its group velocity, which is the derivative of the energy with respect to momentum. The group velocity of a Wave is the Velocity with which the variations in the shape of the wave's amplitude (known as the modulation or envelope In Calculus, a branch of mathematics the derivative is a measurement of how a function changes when the values of its inputs change
where, as above, E and p are the polariton's energy and momentum magnitude, and ω and k are its angular frequency and wave number, respectively. Retinal, technically called retinene1 or retinaldehyde, is a light-sensitive Retinene molecule found in the Photoreceptor cells of In some cases, the dispersion can result in extremely slow speeds of light in matter. Slow light is the literal slowing of the Speed of light. It is the propagation of an optical pulse or other modulation of an optical carrier at a very low Group velocity The effects of photon interactions with other quasi-particles may be observed directly in Raman scattering and Brillouin scattering. Raman scattering or the Raman effect (pronounced — is the inelastic scattering of a Photon. Brillouin scattering, named for Léon Brillouin, occurs when Light in a medium (such as Water or a Crystal) interacts with time dependent
Photons can also be absorbed by nuclei, atoms or molecules, provoking transitions between their energy levels. In Physics, absorption of electromagnetic radiation is the process by which the Energy of a Photon is taken up by matter typically the electrons of an A quantum mechanical system or particle that is bound, confined spacially can only take on certain discrete values of energy as opposed to classical particles which A classic example is the molecular transition of retinal (C20H28O, Figure at right), which is responsible for vision, as discovered in 1958 by Nobel laureate biochemist George Wald and co-workers. Retinal, technically called retinene1 or retinaldehyde, is a light-sensitive Retinene molecule found in the Photoreceptor cells of In Psychology, visual perception is the ability to interpret information from Visible light reaching the Eyes The resulting Perception is also George Wald ( November 18, 1906 &ndash April 12, 1997) was an American Scientist who is best known for his work with pigments As shown here, the absorption provokes a cis-trans isomerization that, in combination with other such transitions, is transduced into nerve impulses. The absorption of photons can even break chemical bonds, as in the photodissociation of chlorine; this is the subject of photochemistry. Photodissociation, photolysis, or photodecomposition is a Chemical reaction in which a Chemical compound is broken down by Photons Chlorine (ˈklɔriːn from the Greek word 'χλωρóς' ( khlôros, meaning 'pale green' is the Chemical element with Atomic number 17 and Photochemistry, a sub-discipline of Chemistry, is the study of the interactions between Atoms, small Molecules, and light (or Electromagnetic radiation
Technological applications
Photons have many applications in technology. These examples are chosen to illustrate applications of photons per se, rather than general optical devices such as lenses, etc. that could operate under a classical theory of light. The laser is an extremely important application and is discussed above under stimulated emission. In Optics, stimulated emission is the process by which an electron perturbed by a Photon having the correct energy may drop to a lower Energy level resulting
Individual photons can be detected by several methods. The classic photomultiplier tube exploits the photoelectric effect: a photon landing on a metal plate ejects an electron, initiating an ever-amplifying avalanche of electrons. Photomultiplier tubes ( photomultipliers or PMT s for short members of the class of Vacuum tubes and more specifically Phototubes are extremely Introduction When a Metallic surface is exposed to Electromagnetic radiation above a certain threshold Frequency, the light is absorbed and Electrons Charge-coupled device chips use a similar effect in semiconductors: an incident photon generates a charge on a microscopic capacitor that can be detected. A charge-coupled device ( CCD) is an analog Shift register, that enables the transportation of analog signals (electric charges through successive stages (capacitors A semiconductor' is a Solid material that has Electrical conductivity in between a conductor and an insulator; it can vary over that Other detectors such as Geiger counters use the ability of photons to ionize gas molecules, causing a detectable change in conductivity. A Geiger counter, also called a Geiger-Müller counter, is a type of Particle detector that measures Ionizing radiation.
Planck's energy formula E = hν is often used by engineers and chemists in design, both to compute the change in energy resulting from a photon absorption and to predict the frequency of the light emitted for a given energy transition. For example, the emission spectrum of a fluorescent light bulb can be designed using gas molecules with different electronic energy levels and adjusting the typical energy with which an electron hits the gas molecules within the bulb. An element's 'emission spectrum' is the relative intensity of Electromagnetic radiation of each Frequency it emits when it is Heated (or more generally when A fluorescent lamp or fluorescent tube is a Gas-discharge lamp that uses Electricity to excite mercury Vapor.
Under some conditions, an energy transition can be excited by two photons that individually would be insufficient. This allows for higher resolution microscopy, because the sample absorbs energy only in the region where two beams of different colors overlap significantly, which can be made much smaller than the excitation volume of a single beam (see two-photon excitation microscopy). Two-photon excitation microscopy is a Fluorescence imaging technique that allows imaging living tissue up to a depth of one millimeter Moreover, these photons cause less damage to the sample, since they are of lower energy.
In some cases, two energy transitions can be coupled so that, as one system absorbs a photon, another nearby system "steals" its energy and re-emits a photon of a different frequency. This is the basis of fluorescence resonance energy transfer, which is used to measure molecular distances. Förster resonance energy transfer (abbreviated FRET) also known as Fluoresence resonance energy transfer or resonance energy transfer ( RET
Recent research
- See also: Quantum optics
The fundamental nature of the photon is believed to be understood theoretically; the prevailing Standard Model predicts that the photon is a gauge boson of spin 1, without mass and without charge, that results from a local U(1) gauge symmetry and mediates the electromagnetic interaction. Quantum optics is a field of research in Physics, dealing with the application of Quantum mechanics to phenomena involving Light and its interactions The Standard Model of Particle physics is a theory that describes three of the four known Fundamental interactions together with the Elementary particles In Mathematics, the unitary group of degree n, denoted U( n) is the group of n × n unitary matrices However, physicists continue to check for discrepancies between experiment and the Standard Model predictions, in the hope of finding clues to physics beyond the Standard Model. In particular, experimental physicists continue to set ever better upper limits on the charge and mass of the photon; a non-zero value for either parameter would be a serious violation of the Standard Model. However, all experimental data hitherto are consistent with the photon having zero charge[15] and mass. [64] The best universally accepted upper limits on the photon charge and mass are 5×10−52 C (or 3×10−33 times the elementary charge) and 1. The coulomb (symbol C) is the SI unit of Electric charge. It is named after Charles-Augustin de Coulomb. The elementary charge, usually denoted e, is the Electric charge carried by a single Proton, or equivalently the negative of the electric charge carried 1×10−52 kg (6x10-17 eV), respectively . [65]
Much research has been devoted to applications of photons in the field of quantum optics. Quantum optics is a field of research in Physics, dealing with the application of Quantum mechanics to phenomena involving Light and its interactions Photons seem well-suited to be elements of an ultra-fast quantum computer, and the quantum entanglement of photons is a focus of research. A quantum computer is a device for Computation that makes direct use of distinctively Quantum mechanical Phenomena, such as superposition Quantum entanglement is a quantum mechanical Phenomenon in which the Quantum states of two or more objects are linked together so that one object Nonlinear optical processes are another active research area, with topics such as two-photon absorption, self-phase modulation and optical parametric oscillators. Nonlinear optics (NLO is the branch of Optics that describes the behaviour of Light in nonlinear media, that is media in which the dielectric polarization Self-phase modulation (SPM is a nonlinear optical effect of Light - Matter interaction An optical parametric oscillator (OPO is a Parametric oscillator which oscillates at optical frequencies However, such processes generally do not require the assumption of photons per se; they may often be modeled by treating atoms as nonlinear oscillators. The nonlinear process of spontaneous parametric down conversion is often used to produce single-photon states. Finally, photons are essential in some aspects of optical communication, especially for quantum cryptography. Optical communication is any form of Telecommunication that uses Light as the transmission medium Quantum cryptography, or quantum key distribution (QKD uses Quantum mechanics to guarantee secure communication
See also
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References and footnotes
- ^ a b B. Light, or visible light, is Electromagnetic radiation of a Wavelength that is visible to the Human eye (about 400–700 Electromagnetic radiation takes the form of self-propagating Waves in a Vacuum or in Matter. Quantum optics is a field of research in Physics, dealing with the application of Quantum mechanics to phenomena involving Light and its interactions Photonics is the science of generating controlling and detecting Photons particularly in the visible and near Infra-red spectrum, but Photon polarization is the quantum mechanical description of the classical polarized sinusoidal plane electromagnetic wave Ballistic photons are the Light Photons that travel through a Scattering ( turbid) medium in a straight line Photography (fә'tɒgrәfi or fә'tɑːgrәfi (from Greek φωτο and γραφία is the process and Art of recording pictures by means of capturing A laser is a device that emits Light ( Electromagnetic radiation) through a process called Stimulated emission. The Advanced Photon Source ( APS) at Argonne National Laboratory is a national Synchrotron -radiation light source research facility funded by the H. Bransden and C. J. Joachain. Quantum Mechanics, 2e, 545. ISBN 0-582-35691-1.
- ^ Official particle table for gauge and Higgs bosons Retrieved October 24, 2006
- ^ a b The mass of the photon is believed to be exactly zero, based on experiment and theoretical considerations described in the article. Events 69 - Second Battle of Bedriacum, forces under Antonius Primus the commander of the Danube armies loyal to Vespasian, defeat Year 2006 ( MMVI) was a Common year starting on Sunday of the Gregorian calendar. Some sources also refer to the "relativistic mass" concept, which is just the energy scaled to units of mass. The term Mass in Special relativity usually refers to the Rest mass of the object which is the Newtonian mass as measured by an observer moving along with For a photon with wavelength λ or energy E, this is h/λc or E/c2. This usage for the term "mass" is no longer common in scientific literature.
- ^ Vimal, R. L. P. , Pokorny, J. , Smith, V. C. , & Shevell, S. K. (1989). Foveal cone thresholds. Vision Res, 29(1), 61-78. http://www.geocities.com/vri98/Vimal-foveal-cone-ratio-VR-1989
- ^ a b c d e Einstein, A (1905). Albert Einstein ( German: ˈalbɐt ˈaɪ̯nʃtaɪ̯n; English: ˈælbɝt ˈaɪnstaɪn (14 March 1879 – 18 April 1955 was a German -born theoretical "Über einen die Erzeugung und Verwandlung des Lichtes betreffenden heuristischen Gesichtspunkt (trans. A Heuristic Model of the Creation and Transformation of Light)". Annalen der Physik 17: 132–148. Annalen der Physik is one of the best-known and oldest (since 1790 Physics journals worldwide (German). An English translation is available from Wikisource. Wikisource is a Wikimedia project to build a free, Wiki Library of Source texts along with translations into any language
- ^ a b c d Einstein, A (1909). Albert Einstein ( German: ˈalbɐt ˈaɪ̯nʃtaɪ̯n; English: ˈælbɝt ˈaɪnstaɪn (14 March 1879 – 18 April 1955 was a German -born theoretical "Über die Entwicklung unserer Anschauungen über das Wesen und die Konstitution der Strahlung (trans. The Development of Our Views on the Composition and Essence of Radiation)". Physikalische Zeitschrift 10: 817–825. (German). An English translation is available from Wikisource. Wikisource is a Wikimedia project to build a free, Wiki Library of Source texts along with translations into any language
- ^ a b Einstein, A (1916a). Albert Einstein ( German: ˈalbɐt ˈaɪ̯nʃtaɪ̯n; English: ˈælbɝt ˈaɪnstaɪn (14 March 1879 – 18 April 1955 was a German -born theoretical "Strahlungs-emission und -absorption nach der Quantentheorie". Verhandlungen der Deutschen Physikalischen Gesellschaft 18: 318. (German)
- ^ a b Einstein, A (1916b). Albert Einstein ( German: ˈalbɐt ˈaɪ̯nʃtaɪ̯n; English: ˈælbɝt ˈaɪnstaɪn (14 March 1879 – 18 April 1955 was a German -born theoretical "Zur Quantentheorie der Strahlung". Mitteilungen der Physikalischen Gesellschaft zu Zürich 16: 47. Also Physikalische Zeitschrift, 18, 121–128 (1917). (German)
- ^ Lewis, GN (1926). Gilbert Newton Lewis ( October 23, 1875 - March 23, 1946) was a famous American physical chemist known for the discovery "The conservation of photons". Nature 118: 874–875. Nature is a prominent Scientific journal, first published on 4 November 1869
- ^ Isaac Asimov (1966). The Neutrino, Ghost Particle of the Atom. Doubleday.
- ^ Isaac Asimov (1968). The Universe From Flat Earth To Quasar. Avon Books.
- ^ Villard, P (1900). Paul Ulrich Villard (1860 &ndash 13 January 1934) was a French Chemist and Physicist, born in Saint-Germain-au-Mont-d'Or 28th of September 1860 "Sur la réflexion et la réfraction des rayons cathodiques et des rayons déviables du radium". Comptes Rendus 130: 1010–1012. (French)
- ^ Villard, P (1900). Paul Ulrich Villard (1860 &ndash 13 January 1934) was a French Chemist and Physicist, born in Saint-Germain-au-Mont-d'Or 28th of September 1860 "Sur le rayonnement du radium". Comptes Rendus 130: 1178–1179. (French)
- ^ Rutherford, E; Andrade ENC (1914). Ernest Rutherford 1st Baron Rutherford of Nelson, OM, PC, FRS (30 August 1871 – 19 October 1937 was a New Zealand Physicist Edward Neville da Costa Andrade FRS ( December 27, 1887 - June 6, 1971) was an English Physicist, writer and "The Wavelength of the Soft Gamma Rays from Radium B". Philosophical Magazine 27: 854–868.
- ^ a b Kobychev, V V; Popov, S B (2005). "Constraints on the photon charge from observations of extragalactic sources". Astronomy Letters 31: 147–151. doi:. A digital object identifier ( DOI) is a permanent identifier given to an Electronic document.
- ^ This property was proved experimentally by Raman in 1931. Raman, C.V. (Oct. Sir Chandrasekhara Venkata Raman, FRS (சந்திரசேகர வெங்கடராமன ( 7 November 1888 &ndash 21 November 1931), Ind. Jour. Phy. 6: 353 ; Raman, C.V. (1931), Nature 128: 576 and 727 ; Raman, C.V. & Bhagavantam, S. Sir Chandrasekhara Venkata Raman, FRS (சந்திரசேகர வெங்கடராமன ( 7 November 1888 &ndash 21 November Sir Chandrasekhara Venkata Raman, FRS (சந்திரசேகர வெங்கடராமன ( 7 November 1888 &ndash 21 November (1932), Nature 129: 22-23, <http://www.nature.com/physics/looking-back/raman2/index.html>.
- ^ Descartes, R (1637). Discours de la méthode (Discourse on Method). Organization How to think correctly The Method of Science Morals Maxims deduced from this Method Proof of God and the Soul Physics the heart (French)
- ^ Hooke, R (1665). Robert Hooke, FRS (18 July 1635 – 3 March 1703 was an English Natural philosopher and Polymath who played an important role in the ' "Micrographia: or some physiological descriptions of minute bodies made by magnifying glasses with observations and inquiries thereupon....
- ^ Huygens, C (1678). Christiaan Huygens (ˈhaɪgənz in English ˈhœyɣəns in Dutch) ( April 14, 1629 &ndash July 8, 1695) was a Dutch Traite de la lumiere (trans. Treatise on Light). (French). An English translation is available from Project Gutenberg
- ^ a b Newton, I (1730). Project Gutenberg, abbreviated as PG, is a volunteer effort to Digitize, archive and distribute Cultural works Sir Isaac Newton, FRS (ˈnjuːtən 4 January 1643 31 March 1727) Biography Early years See also Isaac Newton's early life and achievements Opticks, 4th edition, Dover Publications, Book II, Part III, Propositions XII–XX; Queries 25–29. ISBN 0-486-60205-2.
- ^ Buchwald, Jed Z. (1989). The Rise of the Wave Theory of Light: Optical Theory and Experiment in the Early Nineteenth Century. University of Chicago Press. ISBN 0-226-07886-8.
- ^ Maxwell, JC (1865). James Clerk Maxwell (13 June 1831 &ndash 5 November 1879 was a Scottish mathematician and theoretical physicist. "A Dynamical Theory of the Electromagnetic Field". A Dynamical Theory of the Electromagnetic Field which was written in the year 1864 is the third of James Clerk Maxwell 's papers concerned with Electromagnetism Philosophical Transactions of the Royal Society of London 155: 459–512. This article followed a presentation by Maxwell on 8 December 1864 to the Royal Society. Events 1609 - Biblioteca Ambrosiana opens its reading room the second public library of Europe. Year 1864 ( MDCCCLXIV) was a Leap year starting on Friday (link will display the full calendar of the Gregorian Calendar (or a Leap year
- ^ Hertz, H (1888). Heinrich Rudolf Hertz ( February 22, 1857 – January 1, 1894) was a German physicist who clarified and expanded the electromagnetic theory "Über Strahlen elektrischer Kraft". Sitzungsberichte der Preussischen Akademie der Wissenschaften (Berlin) 1888: 1297–1307. (German)
- ^ a b Wilhelm Wien Nobel Lecture. Delivered 11 December 1911. Events 359 - Honoratus, the first known Prefect of the City of Constantinople, takes office Year 1911 ( MCMXI) was a Common year starting on Sunday (link will display the full calendar of the Gregorian calendar (or a Common year
- ^ Planck, M (1901). "Über das Gesetz der Energieverteilung im Normalspectrum". Annalen der Physik 4: 553–563. Annalen der Physik is one of the best-known and oldest (since 1790 Physics journals worldwide (German)
- ^ a b Max Planck's Nobel Lecture. Delivered 2 June 1920. Events 455 - The Vandals enter Rome, and plunder the city for two weeks Year 1920 ( MCMXX) was a Leap year starting on Thursday (link will display 1920 of the Gregorian calendar
- ^ a b Compton, A (1923). Arthur Holly Compton (September 10 1892 &ndash March 15 1962 was an American physicist and Nobel laureate in physics for his discovery of the Compton effect "A Quantum Theory of the Scattering of X-rays by Light Elements". Physical Review 21: 483–502. Physical Review (frequently abbreviated as Phys Rev) is one of the oldest and most-respected Scientific journals publishing research on all aspects of
- ^ a b c Pais, A (1982). Abraham (Bram Pais (May 19 1918 Amsterdam, The Netherlands &mdash July 28 2000 Copenhagen, Denmark) was a Dutch -born American Subtle is the Lord: The Science and the Life of Albert Einstein. Oxford University Press.
- ^ a b Robert A. Millikan's Nobel Lecture. Delivered 23 May 1924. Events 1430 - Siege of Compiègne: Joan of Arc is captured by the Burgundians while leading an army to relieve Compiègne Year 1924 ( MCMXXIV) was a Leap year starting on Tuesday (link will display the full calendar of the Gregorian calendar.
- ^ Bohr, N; Kramers HA and Slater JC (1924). Niels Henrik David Bohr (nels ˈb̥oɐ̯ˀ in Danish 7 October 1885 – 18 November 1962 was a Danish Physicist who made fundamental contributions to understanding Hendrik Anthony Kramers ( Rotterdam, February 2, 1894 &ndash Oegstgeest, April 24, 1952) was a Dutch Physicist John Clarke Slater (1900-1976 was a noted American physicist and theoretical chemist. "The Quantum Theory of Radiation". Philosophical Magazine 47: 785–802. The Philosophical Magazine is arguably the world’s oldest commercially published Scientific journal. Also Zeitschrift für Physik, 24, 69 (1924). The Zeitschrift für Physik (Journal of Physics was a German Academic journal published from 1920 until 1997
- ^ Heisenberg Nobel lecture, delivered 11 December 1933. Events 359 - Honoratus, the first known Prefect of the City of Constantinople, takes office Year 1933 ( MCMXXXIII) was a Common year starting on Sunday (link will display full calendar of the Gregorian calendar.
- ^ Mandel, L (1976). Leonard Mandel ( May 9, 1927 - February 9 2001) was the Lee DuBridge Professor Emeritus of Physics and Optics at the "The case for and against semiclassical radiation theory". Progress in Optics XIII: 27–69. North-Holland.
- ^ a b These experiments produce results that cannot be explained by any classical theory of light, since they involve anticorrelations that result from the quantum measurement process. The framework of Quantum mechanics requires a careful definition of measurement, and a thorough discussion of its practical and philosophical implications In 1974, the first such experiment was carried out by Clauser, who reported a violation of a classical Cauchy–Schwarz inequality. In Mathematics, the Cauchy–Schwarz inequality, also known as the Schwarz inequality, the Cauchy inequality, or the Cauchy–Schwarz–Bunyakovsky In 1977, Kimble et al. demonstrated an analogous anti-bunching effect of photons interacting with a beam splitter; this approach was simplified and sources of error eliminated in the photon-anticorrelation experiment of Grangier et al. (1986). This work is reviewed and simplified further in Thorn et al. (2004). (These references are listed below under Additional references. )
- ^ Taylor, GI (1909). Sir Geoffrey Ingram Taylor OM ( 7 March 1886 - 27 June 1975) was a Physicist, Mathematician and expert on Fluid dynamics "Interference fringes with feeble light". Proceedings of the Cambridge Philosophical Society 15: 114–115.
- ^ Heisenberg, W (1927). Werner Heisenberg (5 December 1901 in Würzburg &ndash1 February 1976 in Munich) was a German theoretical physicist best known for enunciating the "Über den anschaulichen Inhalt der quantentheoretischen Kinematik und Mechanik". Zeitschrift für Physik 43: 172–198. (German)
- ^ Kramers, HA (1958). Hendrik Anthony Kramers ( Rotterdam, February 2, 1894 &ndash Oegstgeest, April 24, 1952) was a Dutch Physicist Quantum Mechanics. Amsterdam: North-Holland.
- ^ Bohm, D (1954). David Joseph Bohm ( December 20 1917, Wilkes-Barre Pennsylvania – October 27 1992, London) was an American Quantum Theory. London: Constable.
- ^ Newton, TD; Wigner EP (1949). Eugene Paul "EP" Wigner ( Hungarian Wigner Pál Jenő) ( November 17, 1902 &ndash January 1, 1995) was a "Localized states for elementary particles". Reviews of Modern Physics 21: 400–406.
- ^ Bialynicki-Birula, I (1994). "On the wave function of the photon". Acta Physica Polonica A 86: 97–116.
- ^ Sipe, JE (1995). "Photon wave functions". Physical Review A 52: 1875–1883.
- ^ Bialynicki-Birula, I (1996). "Photon wave function". Progress in Optics 36: 245–294.
- ^ Scully, MO; Zubairy MS (1997). Quantum Optics. Cambridge: Cambridge University Press.
- ^ Bose, SN (1924). Satyendra Nath Bose (/sɐθjinðrɐ nɑθ bos/ সত্যেন্দ্র নাথ বসু ( January 1, 1894 &ndash February 4, 1974 "Plancks Gesetz und Lichtquantenhypothese". Zeitschrift für Physik 26: 178–181. The Zeitschrift für Physik (Journal of Physics was a German Academic journal published from 1920 until 1997 (German)
- ^ Einstein, A (1924). Albert Einstein ( German: ˈalbɐt ˈaɪ̯nʃtaɪ̯n; English: ˈælbɝt ˈaɪnstaɪn (14 March 1879 – 18 April 1955 was a German -born theoretical "Quantentheorie des einatomigen idealen Gases". Sitzungsberichte der Preussischen Akademie der Wissenschaften (Berlin), Physikalisch-mathematische Klasse 1924: 261–267. (German)
- ^ Einstein, A (1925). Albert Einstein ( German: ˈalbɐt ˈaɪ̯nʃtaɪ̯n; English: ˈælbɝt ˈaɪnstaɪn (14 March 1879 – 18 April 1955 was a German -born theoretical "Quantentheorie des einatomigen idealen Gases, Zweite Abhandlung". Sitzungsberichte der Preussischen Akademie der Wissenschaften (Berlin), Physikalisch-mathematische Klasse 1925: 3–14. (German)
- ^ Anderson, MH; Ensher JR, Matthews MR, Wieman CE, and Cornell EA (1995). Carl Edwin Wieman (born March 26 1951) is an American Physicist at the University of British Columbia and Nobel Prize in Eric Allin Cornell (born December 19, 1961) is a physicist who along with Carl E "Observation of Bose–Einstein Condensation in a Dilute Atomic Vapor". Science 269: 198–201.
- ^ Dirac, PAM (1926). "On the Theory of Quantum Mechanics". Proc. Roy. Soc. A 112: 661–677.
- ^ a b Dirac, PAM (1927a). "The Quantum Theory of the Emission and Absorption of Radiation". Proc. Roy. Soc. A 114: 243–265.
- ^ a b Dirac, PAM (1927b). "The Quantum Theory of Dispersion". Proc. Roy. Soc. A 114: 710–728.
- ^ Heisenberg, W; Pauli W (1929). Werner Heisenberg (5 December 1901 in Würzburg &ndash1 February 1976 in Munich) was a German theoretical physicist best known for enunciating the "Zur Quantentheorie der Wellenfelder". Zeitschrift für Physik 56: 1. (German)
- ^ Heisenberg, W; Pauli W (1930). Werner Heisenberg (5 December 1901 in Würzburg &ndash1 February 1976 in Munich) was a German theoretical physicist best known for enunciating the "Zur Quantentheorie der Wellenfelder". Zeitschrift für Physik 59: 139. (German)
- ^ Fermi, E (1932). "Quantum Theory of Radiation". Reviews of Modern Physics 4: 87.
- ^ Born, M (1926a). Max Born (11 December 1882 &ndash 5 January 1970 was a German Physicist and Mathematician who was instrumental in the development of Quantum "Zur Quantenmechanik der Stossvorgänge". Zeitschrift für Physik 37: 863–867. (German)
- ^ Born, M (1926b). Max Born (11 December 1882 &ndash 5 January 1970 was a German Physicist and Mathematician who was instrumental in the development of Quantum "Zur Quantenmechanik der Stossvorgänge". Zeitschrift für Physik 38: 803. (German)
- ^ Pais, A (1986). Abraham (Bram Pais (May 19 1918 Amsterdam, The Netherlands &mdash July 28 2000 Copenhagen, Denmark) was a Dutch -born American Inward Bound: Of Matter and Forces in the Physical World. Oxford University Press. Specifically, Born claimed to have been inspired by Einstein's never-published attempts to develop a “ghost-field” theory, in which point-like photons are guided probabilistically by ghost fields that follow Maxwell's equations.
- ^ Debye, P (1910). Peter Joseph William Debye ( March 24 1884 &ndash November 2 1966) was a Dutch physicist and physical chemist "Der Wahrscheinlichkeitsbegriff in der Theorie der Strahlung". Annalen der Physik 33: 1427–34. Annalen der Physik is one of the best-known and oldest (since 1790 Physics journals worldwide (German)
- ^ Born, M; Heisenberg W and Jordan P (1925). Max Born (11 December 1882 &ndash 5 January 1970 was a German Physicist and Mathematician who was instrumental in the development of Quantum Werner Heisenberg (5 December 1901 in Würzburg &ndash1 February 1976 in Munich) was a German theoretical physicist best known for enunciating the Pascual Jordan (b October 18, 1902 in Hanover, Germany; d July 31, 1980 in Hamburg, Federal Republic "Quantenmechanik II". Zeitschrift für Physik 35: 557–615. (German)
- ^ a b Ryder, LH (1996). Quantum field theory, 2nd edition, Cambridge University Press. ISBN 0-521-47814-6.
- ^ Sheldon Glashow Nobel lecture, delivered 8 December 1979. Events 1609 - Biblioteca Ambrosiana opens its reading room the second public library of Europe. Year 1979 ( MCMLXXIX) was a Common year starting on Monday (link displays the 1979 Gregorian calendar)
- ^ Abdus Salam Nobel lecture, delivered 8 December 1979. Events 1609 - Biblioteca Ambrosiana opens its reading room the second public library of Europe. Year 1979 ( MCMLXXIX) was a Common year starting on Monday (link displays the 1979 Gregorian calendar)
- ^ Steven Weinberg Nobel lecture, delivered 8 December 1979. Events 1609 - Biblioteca Ambrosiana opens its reading room the second public library of Europe. Year 1979 ( MCMLXXIX) was a Common year starting on Monday (link displays the 1979 Gregorian calendar)
- ^ QCD and Two-Photon Physics, in Linear Collider Physics Resource Book for Snowmass 2001, Chapter 7, LC-REV-2001-074-US.
- ^ Robert Naeye (1998). Through the Eyes of Hubble: Birth, Life and Violent Death of Stars. CRC Press. ISBN 0750304847.
- ^ (a) Goldhaber, AS (1971). "Terrestrial and Extraterrestrial Limits on The Photon Mass". Reviews of Modern Physics 43: 277–96. The Reviews of Modern Physics is a journal of the American Physical Society. .
(b) Fischbach, E; Kloor H, Langel RA, Lui ATY, and Peredo M (1994). "New Geomagnetic Limits on the Photon Mass and on Long-Range Forces Coexisting with Electromagnetism". Physical Review Letters 73: 514–17. Physical Review Letters is one of the most prestigious journals in Physics. .
(c) Official particle table for gauge and Higgs bosons S. Eidelman et al. (Particle Data Group) Physics Letters B 592, 1 (2004)
(d) Davis, L; Goldhaber AS and Nieto MM (1975). "Limit on Photon Mass Deduced from Pioneer-10 Observations of Jupiter's Magnetic Field". Physical Review Letters 35: 1402–1405. .
(e) Luo, J; Shao CG, Liu ZZ, and Hu ZK (1999). "Determination of the limit of photon mass and cosmic magnetic vector with rotating torsion balance". Physical Review A 270: 288–292. .
(f) Schaeffer, BE (1999). "Severe limits on variations of the speed of light with frequency". Physical Review Letters 82: 4964–4966. .
(g) Luo, J; Tu LC, Hu ZK, and Luan EJ (2003). "New experimental limit on the photon rest mass with a rotating torsion balance". Physical Review Letters 90: Art. No. 081801.
(h) Williams, ER; Faller JE and Hill HA (1971). "New Experimental Test of Coulomb's Law: A Laboratory Upper Limit on the Photon Rest Mass". Physical Review Letters 26: 721–724.
(i) Lakes, R (1998). "Experimental Limits on the Photon Mass and Cosmic Magnetic Vector Potential". Physical Review Letters 80: 1826.
(j) 2006 PDG listing for photon W. -M. Yao et al. (Particle Data Group) Journal of Physics G 33, 1 (2006).
(k) Adelberger, E; Dvali, G and Gruzinov, A. "Photon Mass Bound Destroyed by Vortices". Physical Review Letters 98: Art. No. 010402. - ^ Official particle table for gauge and Higgs bosons Retrieved October 24, 2006
Additional references
- Clauser, JF. Events 69 - Second Battle of Bedriacum, forces under Antonius Primus the commander of the Danube armies loyal to Vespasian, defeat Year 2006 ( MMVI) was a Common year starting on Sunday of the Gregorian calendar. (1974). "Experimental distinction between the quantum and classical field-theoretic predictions for the photoelectric effect". Phys. Rev. D 9: 853–860.
- Kimble, HJ; Dagenais M, and Mandel L. (1977). "Photon Anti-bunching in Resonance Fluorescence". Phys. Rev. Lett. 39: 691–695. article web link
- Grangier, P; Roger G, and Aspect A. (1986). "Experimental Evidence for a Photon Anticorrelation Effect on a Beam Splitter: A New Light on Single-Photon Interferences". Europhysics Letters 1: 501–504.
- Thorn, JJ; Neel MS, Donato VW, Bergreen GS, Davies RE and Beck M. (2004). "Observing the quantum behavior of light in an undergraduate laboratory". American Journal of Physics 72: 1210–1219. http://people.whitman.edu/~beckmk/QM/grangier/grangier.html
- Pais, A. (1982). Abraham (Bram Pais (May 19 1918 Amsterdam, The Netherlands &mdash July 28 2000 Copenhagen, Denmark) was a Dutch -born American Subtle is the Lord: The Science and the Life of Albert Einstein. Oxford University Press. An excellent history of the photon's early development.
- Roy Glauber's Nobel Lecture, “100 Years of Light Quanta”. Delivered 8 December 2005. Events 1609 - Biblioteca Ambrosiana opens its reading room the second public library of Europe. Year 2005 ( MMV) was a Common year starting on Saturday (link displays full calendar of the Gregorian calendar. Another history of the photon, summarized by a key physicist who developed the concepts of coherent states of photons. In Quantum mechanics a coherent state is a specific kind of quantum state of the Quantum harmonic oscillator whose dynamics most closely resemble the oscillating behaviour
- Lamb, WE (1995). Willis Eugene Lamb Jr ( July 12, 1913 &ndash May 15, 2008) was a Physicist who won the Nobel Prize in Physics in "Anti-photon". Applied Physics B 60: 77–84. Feisty, fun and sometimes snarky history of the photon, with a strong argument for allowing only its second-quantized definition, by Willis Lamb, the 1955 Nobel laureate in Physics. Willis Eugene Lamb Jr ( July 12, 1913 &ndash May 15, 2008) was a Physicist who won the Nobel Prize in Physics in The Nobel Prize in Physics (Nobelpriset i fysik is awarded once a year by the Royal Swedish Academy of Sciences.
- Special supplemental issue of Optics and Photonics News (vol. 14, October 2003)
- Roychoudhuri, C; Rajarshi R. "The nature of light: what is a photon?". Optics and Photonics News 14: S1 (Supplement).
- Zajonc, A. "Light reconsidered". Optics and Photonics News 14: S2–S5 (Supplement).
- Loudon, R. "What is a photon?". Optics and Photonics News 14: S6–S11 (Supplement).
- Finkelstein, D. "What is a photon?". Optics and Photonics News 14: S12–S17 (Supplement).
- Muthukrishnan, A; Scully MO, Zubairy MS. "The concept of the photon—revisited". Optics and Photonics News 14: S18–S27 (Supplement).
- Mack, H; Schleich WP. "A photon viewed from Wigner phase space". Optics and Photonics News 14: S28–S35 (Supplement).
Dictionary
photon
-noun
- (physics) The quantum of light and other electromagnetic energy, regarded as a discrete particle having zero rest mass, no electric charge, and an indefinitely long lifetime. It is a gauge boson.
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