In physics wavelength is the distance between repeating units of a propagating wave of a given frequency. Physics (Greek Physis - φύσις in everyday terms is the Science of Matter and its motion. A wave is a disturbance that propagates through Space and Time, usually with transference of Energy. Frequency is a measure of the number of occurrences of a repeating event per unit Time. It is commonly designated by the Greek letter lambda (λ). Greek (el ελληνική γλώσσα or simply el ελληνικά — "Hellenic" is an Indo-European language, spoken today by 15-22 million people mainly A letter is an element in an Alphabetic system of writing such as the Greek alphabet and its descendants Lambda (uppercase Λ, lowercase λ; Λάμβδα or el Λάμδα Lamda is the 11th letter of the Greek alphabet. Examples of wave-like phenomena are light, water waves, and sound waves. Light, or visible light, is Electromagnetic radiation of a Wavelength that is visible to the Human eye (about 400–700 Ocean surface waves are Surface waves that occur on the Free surface of the Ocean. An acoustic wave is a weak compression wave (meaning a small pressure change that moves at the Speed of sound. The wavelength is related to the frequency by the formula: wavelength = wave speed / frequency. Wavelength is therefore inversely proportional to frequency. Higher frequencies have shorter wavelengths. Lower frequencies have longer wavelengths, assuming the speed of the wave is the same.
In a wave, properties vary with position. For example, in a sound wave the air pressure oscillates, while in light and other electromagnetic radiation the strength of the electric and the magnetic field vary. Sound' is Vibration transmitted through a Solid, Liquid, or Gas; particularly sound means those vibrations composed of Frequencies Sound pressure is the local Pressure deviation from the ambient (average or equilibrium pressure caused by a Sound Wave. 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. 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
Visible light ranges from deep red, roughly 700 nm, to violet, roughly 400 nm (430–750 THz). A nanometre ( American spelling: nanometer, symbol nm) ( Greek: νάνος nanos dwarf; μετρώ metrό count) is a Electromagnetic waves sent at terahertz frequencies, known as terahertz radiation, submillimeter radiation, terahertz waves, terahertz For other examples, see electromagnetic spectrum. The electromagnetic (EM spectrum is the range of all possible Electromagnetic radiation frequencies The wavelengths of sound frequencies audible to the human ear (20 Hz–20 kHz) are between approximately 17 m and 17 mm, respectively. The hertz (symbol Hz) is a measure of Frequency, informally defined as the number of events occurring per Second. The metre or meter is a unit of Length. It is the basic unit of Length in the Metric system and in the International The Millimetre ( American spelling: millimeter, symbol mm) is a unit of Length in the Metric system, equal to So the wavelengths in audible sound are much longer than those in visible light.
Contents |
Relationship with frequency
Wavelength λ is determined using the formula: λ = velocity divided by the frequency. In the case of electromagnetic radiation, such as light, in a vacuum, this velocity is the speed of light, 299,792,458 m/s or about 3×108 m/s. Electromagnetic radiation takes the form of self-propagating Waves in a Vacuum or in Matter. Scientific notation, also sometimes known as standard form or as exponential notation, is a way of writing numbers that accommodates values too large or small to be For sound waves in air, this is the speed of sound, 345 m/s (1238 km/h) in air at room temperature and atmospheric pressure. An acoustic wave is a weak compression wave (meaning a small pressure change that moves at the Speed of sound. Sound is a vibration that travels through an elastic medium as a Wave. In Physical sciences standard conditions for temperature and pressure are Standard sets of conditions for experimental measurements to allow comparisons to be made Usually, SI units are used, where the wavelength is expressed in metres, the frequency in Hz, and the propagation velocity in metres per second. The metre or meter is a unit of Length. It is the basic unit of Length in the Metric system and in the International The hertz (symbol Hz) is a measure of Frequency, informally defined as the number of events occurring per Second. The second ( SI symbol s) sometimes abbreviated sec, is the name of a unit of Time, and is the International System of Units
For example, the wavelength for a 100 MHz electromagnetic (radio) wave is about: λ = 3×108 m/s divided by 100×106 Hz = 3 metres. Electronic engineers often use a shortcut formula: wavelength λ in metres = 300 Mm/s divided by the frequency in MHz, to avoid counting the (many) zero digits in the decimal or scientific notations. A megametre ( American spelling: megameter, symbol Mm) is a unit of Length in the Metric system, equal to one million This article gives a mathematical definition For a more accessible article see Decimal. Scientific notation, also sometimes known as standard form or as exponential notation, is a way of writing numbers that accommodates values too large or small to be
It should be noted that for many wave phenomena, wavelength is not the distance that particles travel during a period. Frequency is a measure of the number of occurrences of a repeating event per unit Time. For instance, in acoustics and water waves, the particle displacements during a period are only a small fraction of the wavelength, apart from extreme conditions like breaking waves and shock waves. Acoustics is the interdisciplinary science that deals with the study of Sound, Ultrasound and Infrasound (all mechanical waves in gases liquids and solids Ocean surface waves are Surface waves that occur on the Free surface of the Ocean. In Physics, a breaking wave is a Wave whose Amplitude reaches a critical level at which some process can suddenly start to occur that causes large amounts For the music album by Converter see Shock Front For the 1977 horror film see Shock Waves A shock wave (also called
It should also be noted that frequency can change without a change in wavelength, but it means that the speed of the wave will change. For example, when light enters another media, its speed and wavelength change, however, its frequency does not, or a change in color would be seen.
In non-vacuum media
The speed of light in most media is lower than in vacuum, which means that the same frequency will correspond to a shorter wavelength in the medium than in vacuum. The wavelength in the medium is
where n is the refractive index of the medium. 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 Wavelengths of electromagnetic radiation are usually quoted in terms of the vacuum wavelength, unless specifically indicated as the "wavelength in the medium". In acoustics, where a medium is essential for the waves to exist, the term wavelength is always the wavelength in the medium. Then the refractive index depends on the mean properties of the medium, for instance the mean pressure or changes in the material composition.
De Broglie wavelength of particles
Louis de Broglie postulated that all particles with momentum have a wavelength
where h is Planck's constant, and p is the momentum of the particle. Louis-Victor-Pierre-Raymond 7th duc de Broglie, FRS (də bʁœj ( August 15 1892 &ndash March 19 1987) was a French In Classical mechanics, momentum ( pl momenta SI unit kg · m/s, or equivalently N · s) is the product The Planck constant (denoted h\ is a Physical constant used to describe the sizes of quanta. In Classical mechanics, momentum ( pl momenta SI unit kg · m/s, or equivalently N · s) is the product This hypothesis was at the basis of quantum mechanics. Quantum mechanics is the study of mechanical systems whose dimensions are close to the Atomic scale such as Molecules Atoms Electrons Nowadays, this wavelength is called the de Broglie wavelength. In Physics, the de Broglie hypothesis (pronounced /brœj/ as French breuil close to "broy" is the statement that all Matter (any object has a Wave For example, the electrons in a CRT display have a De Broglie wavelength of about 10-13 m. The electron is a fundamental Subatomic particle that was identified and assigned the negative charge in 1897 by J The cathode ray tube (CRT is a Vacuum tube containing an Electron gun (a source of electrons and a Fluorescent screen with internal or
See also
- Amplitude
- Angular frequency
- Frequency
- Fraunhofer lines, spectral lines traditionally used as standard optical wavelength references
- Periodic function
- Wave vector
External links
- Conversion: Wavelength to Frequency and vice versa - Sound waves and radio waves
- Teaching resource for 14-16yrs on sound including wavelength
Dapyx Software network: MP3 Explorer | Ebook Manager | Zenithic