Copyright © Philip M. Parker, INSEAD. Terms of Use.
| Domain | Definition |
Aerospace | The emission of an electron from a surface as the surface absorbs a photon of electromagnetic radiation. Electrons so emitted are termed photoelectrons.The effectiveness of the process depends upon the surface metal concerned and the wavelength of the radiant energy to which it is expressed. Cesium, for example, will emit electrons when exposed to visible radiation. The energy of the electron produced is equal to the energy of the incident photon minus the amount of work needed to raise the electron to a sufficient energy level to free it from the surface. The resulting energy of the electron, therefore, is proportional to the frequency (i.e., inversely proportional to the wavelength) of the incident radiation. (references) |
Physics | An effect explained by A. Einstein which demonstrates that light seems to be made up of particles, or photons. Light can excite electrons (called photoelectrons in this context) to be ejected from a metal. Light with a frequency below a certain threshold, at any intensity, will not cause any photoelectrons to be emitted from the metal. Above that frequency, photoelectrons are emitted in proportion to the intensity of incident light.The reason is that a photon has energy in proportion to its wavelength, and the constant of proportionality is the Planck constant. Below a certain frequency -- and thus below a certain energy -- the incident photons do not have enough energy to knock the photoelectrons out of the metal. Above that threshold energy, called the work function, photons will knock the photoelectrons out of the metal, in proportion to the number of photons (the intensity of the light). At higher frequencies and energies, the photoelectrons ejected obtain a kinetic energy corresponding to the difference between the photon's energy and the work function. (references) |
Source: compiled by the editor from various references; see credits. | |
(From Wikipedia, the free Encyclopedia)
The photoelectric effect is the flow of electric current in a material or through a vacuum (as in a photocell) when the material is exposed to light (i.e., a high frequency electromagnetic wave). The photoelectric effect helped further the idea of wave-particle duality, the concept that physical systems can display both wave-like and particle-like properties, and that was used as a fundamental principle by the creators of quantum mechanics. A complete picture of the photoelectric effect was only obtained after the maturity of quantum mechanics.
The phenomenon was difficult to understand in terms of the classic wave description of light, as the energy of the emitted electrons did not depend on the intensity of the incoming light. For a given material, there would be a wavelength threshold: radiant light energy longer than this wavelength, no matter what its intensity, did not produce the effect. In the photoelectric effect, a metal plate is struck by light and emits electrons; the energy of those electrons is determined by the light's frequency, while the number of the electrons is determined by the light's intensity. This effect cannot easily be explained if light is assumed to be a wave.
In 1901 on November 5, Nikola Tesla recieved the patent US685957 (Apparatus for the Utilization of Radiant Energy) that describes radiation charging and discharging conductors (ex., a metal plate) by "radiant energy". Radiant energy throws off with great velocity minute particles (i.e., "electrons") which are strongly electrified. Rays or radiation falling on insulated-conductor connected to a condenser (i.e., a capacitor), the condenser indefinitely charges electrically. The patent specified that the radiation (or radiant energy) include many different forms. These devices have been refered to as "Photoelectric alternating current stepping motors".
Although the effect itself had been described earlier by Nikola Tesla in the patent US685957, Albert Einstein's simple description (in 1905) on how it was caused by absorption of photons, or quanta of light, in the interaction of light with the electrons in the substance helped him win the Nobel Prize. The paper, named "On a Heuristic Viewpoint Concerning the Production and Transformation of Light", proposed the simple description of "light quanta" (now called photons) and showed how they could be used to explain such phenomena as the photoelectric effect. The simple explanation by Einstein in terms of absorption of single quanta of light explained the features of the phenomenon and helped explained the characteristic energy.
The idea of light quanta was motivated by Max Planck's earlier derivation of the law of blackbody radiation by assuming that luminous energy could only be absorbed or emitted in discrete amounts, called quanta. Einstein showed that, by assuming that light actually consisted of discrete packets, he could explain the photoelectric effect. The idea of light quanta contradicted the wave theory of light that followed naturally from James Clerk Maxwell's equations for electromagnetic behavior and, more generally, the assumption of infinite divisibility of energy in physical systems. Even after experiments showed that Einstein's equations for the photoelectric effect were accurate, his explanation was not universally accepted.
The photons of the light beam have a characteristic energy given by the wavelength of the light. In the photoemission process, if an electron absorbs the energy of one photon and has more energy than the work function, it is ejected from the material. If the photon energy is too low, however, the electron is unable to escape the surface of the material. Increasing the intensity of the light beam does not change the energy of the constituent photons, only their number, and thus the energy of the emitted electrons does not depend on the intensity of the incoming light. It was for this insight that Einstein won his only Nobel Prize.
The photoelectric effect is used for solar power by mounting arrays of solar cells which generate direct current from sunlight.
See also
Source: adapted by the editor from Wikipedia, the free encyclopedia under a copyleft GNU Free Documentation License (GFDL) from the article "Photoelectric effect."
Crosswords: PHOTOELECTRIC EFFECT |
| Specialty definitions using "PHOTOELECTRIC EFFECT": photoelectric receptor ♦ relativity, Theory of. (references) |
| The following statistics estimate the number of searches per day across the major English-language search engines as identified by various trade publications. Hyperlinks lead to commercial use of the expression at Amazon.com. |
| Expression | Frequency per Day |
photoelectric effect | 52 |
| Source: compiled by the editor from various references; see credits. | |
| Language | Translations for "PHOTOELECTRIC EFFECT"; alternative meanings/domain in parentheses. | ||||||||||||||||
Danish | i det nedre energiomraade skyldes absorptionen af roentgenstraalingsenergi i luft naesten udelukkende den fotoelektriske effekt (in the lower energy range, the absorption of X-radiation energy by air is almost entirely due to the photoelectric effect), elektroner emitteret fra vaeggen ved den fotoelektriske effekt (electrons emitted by photoelectric effect from the wall). (various references) | ||||||||||||||||
Dutch | in het gebied van de lage energieen wordt de absorptie van rontgenstraling in lucht vrijwel geheel veroorzaakt door het foto-elektrische effect (in the lower energy range, the absorption of X-radiation energy by air is almost entirely due to the photoelectric effect), elektronen welke door het foto-elektrische effect uit de wand vrijkomen (electrons emitted by photoelectric effect from the wall). (various references) | ||||||||||||||||
French | dans la région de basse énergie l'absorption de l'énergie des rayons X par l'air est due presque exclusivement l'effet photoélectrique (the absorption of X-radiation energy by air is almost entirely due to the photoelectric effect). (various references) | ||||||||||||||||
German | im unteren Energiebereich wird die Absorption von Rontgenstrahlungsenergie durch Luft fast ausschliesslich durch den photoelektrischen Effekt bewirkt (in the lower energy range, the absorption of X-radiation energy by air is almost entirely due to the photoelectric effect), Elektronen, die durch den photoelektrischen Effekt aus der Wand freigesetzt werden (electrons emitted by photoelectric effect from the wall). (various references) | ||||||||||||||||
Greek | Ηλεκτρόνια εκπέμπονταν με φωτοηλεκτρικό φαινόμενο από τα τοιχώματα. (electrons emitted by photoelectric effect from the wall), Στις περιοχές χαμηλής ενέργειας,η απορρόφηση της ενέργειας των ακτί-νων Χ από τον αέρα οφείλεται σχεδόν εξ ολοκλήρου στο φωτοηλεκτρικό φαι (in the lower energy range, the absorption of X-radiation energy by air is almost entirely due to the photoelectric effect). (various references) | ||||||||||||||||
Italian | nel campo delle basse energie, l'assorbimento di energia dei raggi X da parte dell'aria è dovuto quasi interamente all'effetto fotoelettrico (in the lower energy range, the absorption of X-radiation energy by air is almost entirely due to the photoelectric effect), elettroni emessi dalla parete per effetto fotoelettrico (electrons emitted by photoelectric effect from the wall). (various references) | ||||||||||||||||
Pig Latin | otoelectricphay effectay na zona de baixa energia,a absorção de radiação-x pelo ar deve-se quase inteiramente,ao efeito fotoeléctrico (in the lower energy range, the absorption of X-radiation energy by air is almost entirely due to the photoelectric effect), electrões emitidos pela parede por efeito fotoeléctrico (electrons emitted by photoelectric effect from the wall). (various references) en el margen inferior de energía, la absorción de la energía de la radiación X por el aire, es debida casi en su totalidad al efecto fotoeléctrico (in the lower energy range, the absorption of X-radiation energy by air is almost entirely due to the photoelectric effect), electrones emitidos por efecto fotoeléctrico desde la pared (electrons emitted by photoelectric effect from the wall). (various references) | ||||||||||||||||
Misspellings | |
"PHOTOELECTRIC EFFECT" is suggested in spellcheckers for the following: photoelecric effect. (additional references) | |
| Source: compiled by the editor, based on several corpora (additional references). | |
| 1. Crosswords 2. Expressions: Internet 3. Translations: Modern 4. Derivations | 5. Bibliography |
Copyright © Philip M. Parker, INSEAD. Terms of Use.
