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"Quanta" redirects here. For other uses, see Quantum (disambiguation).

In physics, a quantum (plural: quanta) is an indivisible entity of a quantity that has the same units as the Planck constant and is related to both energy and momentum of elementary particles of matter (called fermions) and of photons and other bosons. Physics (Greek Physis - φύσις in everyday terms is the Science of Matter and its motion. An entity is something that has a distinct separate Existence, though it need not be a material existence The Planck constant (denoted h\ is a Physical constant used to describe the sizes of quanta. 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 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 Matter is commonly defined as being anything that has mass and that takes up space. In Particle physics, fermions are particles which obey Fermi-Dirac statistics; they are named after Enrico Fermi. In Physics, the photon is the Elementary particle responsible for electromagnetic phenomena In Particle physics, bosons are particles which obey Bose-Einstein statistics; they are named after Satyendra Nath Bose and Albert Einstein The word comes from the Latin "quantus," for "how much. Latin ( lingua Latīna, laˈtiːna is an Italic language, historically spoken in Latium and Ancient Rome. " Behind this, one finds the fundamental notion that a physical property may be "quantized", referred to as "quantization". In Physics, quantization is a procedure for constructing a Quantum field theory starting from a classical field theory. This means that the magnitude can take on only certain discrete numerical values, rather than any value, at least within a range. A number is an Abstract object, tokens of which are Symbols used in Counting and measuring. There is a related term of quantum number. Quantum numbers describe values of conserved numbers in the dynamics of the Quantum system.

A photon is often referred to as a "light quantum. In Physics, the photon is the Elementary particle responsible for electromagnetic phenomena In Physics, the photon is the Elementary particle responsible for electromagnetic phenomena " The energy of an electron bound to an atom (at rest) is said to be quantized, which results in the stability of atoms, and of matter in general. The electron is a fundamental Subatomic particle that was identified and assigned the negative charge in 1897 by J History See also Atomic theory, Atomism The concept that matter is composed of discrete units and cannot be divided into arbitrarily tiny Matter is commonly defined as being anything that has mass and that takes up space. But these terms can be a little misleading, because what is quantized is this Planck's constant quantity whose units can be viewed as either energy multiplied by time or momentum multiplied by distance. The Planck constant (denoted h\ is a Physical constant used to describe the sizes of quanta.

Usually referred to as quantum "mechanics," it is regarded by virtually every professional physicist as the most fundamental framework we have for understanding and describing nature at the infinitesimal level, for the very practical reason that it works. It is "in the nature of things", not a more or less arbitrary human preference.

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Development of quantum theory

Quantum theory, the branch of physics which is based on quantization, began in 1900 when Max Planck published his theory explaining the emission spectrum of black bodies. Quantum mechanics is the study of mechanical systems whose dimensions are close to the Atomic scale such as Molecules Atoms Electrons Year 1900 ( MCM) was an exceptional Common year starting on Monday (link will display the full calendar of the Gregorian calendar 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 In Physics, a black body is an object that absorbs all light that falls on it In that paper Planck used the Natural system of units he invented the previous year. Planck units are Units of measurement named after the German physicist Max Planck, who first proposed them in 1899 Year 1898 ( MDCCCXCVIII) was a Common year starting on Saturday (link will display the full calendar of the Gregorian calendar (or a Common The consequences of the differences between classical and quantum mechanics quickly became obvious. Classical mechanics is used for describing the motion of Macroscopic objects from Projectiles to parts of Machinery, as well as Astronomical objects Quantum mechanics is the study of mechanical systems whose dimensions are close to the Atomic scale such as Molecules Atoms Electrons But it was not until 1926, by the work of Werner Heisenberg, Erwin Schrödinger, and others, that quantum mechanics became correctly formulated and understood mathematically. Year 1926 ( MCMXXVI) was a Common year starting on Friday (link will display the full calendar of the Gregorian calendar. 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 Despite tremendous experimental success, the philosophical interpretations of quantum theory are still widely debated.

Planck was reluctant to accept the new idea of quantization, as were many others. But, with no acceptable alternative, he continued to work with the idea, and found his efforts were well received. Eighteen years later, when he accepted the Nobel Prize in Physics for his contributions, he called it "a few weeks of the most strenuous work" of his life. The Nobel Prize in Physics (Nobelpriset i fysik is awarded once a year by the Royal Swedish Academy of Sciences. During those few weeks, he even had to discard much of his own theoretical work from the preceding years. Quantization turned out to be the only way to describe the new and detailed experiments which were just then being performed. He did this practically overnight, openly reporting his change of mind to his scientific colleagues, in the October, November, and December meetings of the German Physical Society, in Berlin, where the black body work was being intensely discussed. The Deutsche Physikalische Gesellschaft ( DPG, German Physical Society is the world's largest organization of physicists Berlin is the capital city and one of sixteen states of Germany. In this way, careful experimentalists (including Friedrich Paschen, O.R. Lummer, Ernst Pringsheim, Heinrich Rubens, and F. Kurlbaum), and a reluctant theorist, ushered in a momentous scientific revolution. Louis Karl Heinrich Friedrich Paschen ( January 22, 1865 - February 25, 1947) was a German Physicist, known for his work Otto Richard Lummer (1860-1925 was a German physicist and researcher Ernst Prings Heim: Ernst Pringsheim Sr or Ernst Pringsheim sen Heinrich Rubens ( 30 March 1865 - 17 July 1922) was a German Physicist. Ferdinand Kurlbaum ( October 4, 1857, Burg bei Magdeburg - July 29, 1927, Berlin) was a German Physicist

The quantum black-body radiation formula

When a body is heated, it emits radiant heat, a form of electromagnetic radiation in the infrared region of the EM spectrum. Thermal radiation is Electromagnetic radiation emitted from the surface of an object which is due to the object's Temperature. In Physics, heat, symbolized by Q, is Energy transferred from one body or system to another due to a difference in Temperature Electromagnetic radiation takes the form of self-propagating Waves in a Vacuum or in Matter. Infrared ( IR) radiation is Electromagnetic radiation whose Wavelength is longer than that of Visible light, but shorter than that of The electromagnetic (EM spectrum is the range of all possible Electromagnetic radiation frequencies All of this was well understood at the time, and of considerable practical importance. When the body becomes red-hot, the red wavelength parts start to become visible. In Physics wavelength is the distance between repeating units of a propagating Wave of a given Frequency. This had been studied over the previous years, as the instruments were being developed. However, most of the heat radiation remains infrared, until the body becomes as hot as the surface of the Sun (about 6000 °C, where most of the light is green in color). The Sun (Sol is the Star at the center of the Solar System. This was not achievable in the laboratory at that time. What is more, measuring specific infrared wavelengths was only then becoming feasible, due to newly developed experimental techniques. Until then, most of the electromagnetic spectrum was not measurable, and therefore blackbody emission had not been mapped out in detail. The electromagnetic (EM spectrum is the range of all possible Electromagnetic radiation frequencies

The quantum black-body radiation formula, being the very first piece of quantum mechanics, appeared Sunday evening October 7, 1900, in a so-called back-of-the-envelope calculation by Planck. It was based on a report by Rubens (visiting with his wife) of the very latest experimental findings in the infrared. Heinrich Rubens ( 30 March 1865 - 17 July 1922) was a German Physicist. Later that evening, Planck sent the formula on a postcard, which Rubens received the following morning. A couple of days later, he informed Planck that it worked perfectly. At first, it was just a fit to the data; only later did it turn out to enforce quantization.

This second step was only possible due to a certain amount of luck (or skill, even though Planck himself called it "a fortuitous guess at an interpolation formula"). It was during the course of polishing the mathematics of his formula that Planck stumbled upon the beginnings of Quantum Theory. Briefly stated, he had two mathematical expressions:

Combining these as x(a+x), he still has x, approximately, when x is much smaller than a (the red end of the spectrum); but now also x² (again approximately) when x is much larger than a (in the infrared). The formula for the energy E, in a single mode of radiation at frequency λ, and temperature T, can be written

E = \frac{h \lambda}{e^{\frac{h \lambda}{k T}} - 1}

This is (essentially) what is being compared with the experimental measurements. There are two parameters to determine from the data, written in the present form by the symbols used today: h is the new Planck's constant, and k is Boltzmann's constant. The Planck constant (denoted h\ is a Physical constant used to describe the sizes of quanta. Bridge from macroscopic to microscopic physics Boltzmann's constant k is a bridge between Macroscopic and microscopic physics Both have now become fundamental in physics, but that was by no means the case at the time. The "elementary quantum of energy" is hλ. But such a unit does not normally exist, and is not required for quantization.

Beyond electromagnetic radiation

While quantization was first discovered in electromagnetic radiation, it describes a fundamental aspect of energy not just restricted to photons. [1]

The birthday of quantum mechanics

From the experiments, Planck deduced the numerical values of h and k. Thus he could report, in the German Physical Society meeting on December 14, 1900, where quantization (of energy) was revealed for the first time, values of the Avogadro-Loschmidt number, the number of real molecules in a mole, and the unit of electrical charge, which were more accurate than those known until then. The Avogadro constant (symbols L, N A also called Avogadro's number, is the number of "elementary entities" (usually Atoms The mole (symbol mol) is a unit of Amount of substance: it is an SI base unit, and almost the only unit to be used to measure this Electric charge is a fundamental conserved property of some Subatomic particles which determines their Electromagnetic interaction. This event has been referred to as "the birth of quantum mechanics".

See also

References

Notes

  1. ^ Real-World Quantum Effects Demonstrated February 11, 2005

Dictionary

quantum

-noun

  1. (archaic except in South Asian dialects) Quantity, amount.
  2. (physics) The smallest possible, and therefore indivisible, unit of a given quantity or quantifiable phenomenon.

-adjective

  1. Of a change, significant
  2. (physics) Involving quanta
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