AskDefine | Define photoelectric

Dictionary Definition

photoelectric adj : of or pertaining to photoelectricity; "the photoelectric effect" [syn: photoelectrical]

User Contributed Dictionary

English

Adjective

  1. Of, or relating to the electric effects of electromagnetic radiation

Related terms

Extensive Definition

The photoelectric effect is a quantum electronic phenomenon in which electrons are emitted from matter after the absorption of energy from electromagnetic radiation such as x-rays or visible light. The emitted electrons can be referred to as photoelectrons in this context. The effect is also termed the Hertz Effect, due to its discovery by Heinrich Rudolf Hertz, although the term has generally fallen out of use.
Study of the photoelectric effect led to important steps in understanding the quantum nature of light and electrons and influenced the formation of the concept of wave–particle duality.
  1. Inner photoelectric effect (see photodiode below). The hole left behind can give rise to auger effect, which is visible even when the electron does not leave the material. In molecular solids photons are excited in this step and may be visible as lines in the final electron energy. The inner photoeffect has to be dipole allowed. The transition rules for atoms translate via the tight-binding model onto the crystal. They are similar in geometry to plasma oscillations in that they have to be transversal.
  2. Ballistic transport of half of the electrons to the surface. Some electrons are scattered.
  3. Electrons escape from the material at the surface.
In the three-step model, an electron can take multiple paths through these three steps. All paths can interfere in the sense of the path integral formulation. For surface states and molecules the three-step model does still make some sense as even most atoms have multiple electrons which can scatter the one electron leaving.

History

Early observations

In 1839, Alexandre Edmond Becquerel observed the photoelectric effect via an electrode in a conductive solution exposed to light. In 1873, Willoughby Smith found that selenium is photoconductive.

Hertz's spark gaps

In 1887, Heinrich Hertz observed the photoelectric effect and the production and reception of electromagnetic (EM) waves. He published these observations in the journal Annalen der Physik. His receiver consisted of a coil with a spark gap, where a spark would be seen upon detection of EM waves. He placed the apparatus in a darkened box to see the spark better. However, he noticed that the maximum spark length was reduced when in the box. A glass panel placed between the source of EM waves and the receiver absorbed ultraviolet radiation that assisted the electrons in jumping across the gap. When removed, the spark length would increase. He observed no decrease in spark length when he substituted quartz for glass, as quartz does not absorb UV radiation. Hertz concluded his months of investigation and reported the results obtained. He did not further pursue investigation of this effect, nor did he make any attempt at explaining how this phenomenon was brought about.

JJ Thomson: electrons

In 1899, J. J. Thomson investigated ultraviolet light in Crookes tubes. Influenced by the work of James Clerk Maxwell, Thomson deduced that cathode rays consisted of negatively charged particles, later called electrons, which he called "corpuscles". In the research, Thomson enclosed a metal plate (a cathode) in a vacuum tube, and exposed it to high frequency radiation. It was thought that the oscillating electromagnetic fields caused the atoms' field to resonate and, after reaching a certain amplitude, caused a subatomic "corpuscle" to be emitted, and current to be detected. The amount of this current varied with the intensity and color of the radiation. Larger radiation intensity or frequency would produce more current.
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Applets
photoelectric in Arabic: مفعول كهرضوئي
photoelectric in Bengali: আলোক তড়িৎ ক্রিয়া
photoelectric in Bosnian: Fotoelektrični efekat
photoelectric in Bulgarian: Фотоелектричен ефект
photoelectric in Catalan: Efecte fotoelèctric
photoelectric in Czech: Fotoelektrický jev
photoelectric in Danish: Fotoelektrisk effekt
photoelectric in German: Photoelektrischer Effekt
photoelectric in Estonian: Fotoefekt
photoelectric in Modern Greek (1453-): Φωτοηλεκτρικό φαινόμενο
photoelectric in Spanish: Efecto fotoeléctrico
photoelectric in Esperanto: Fotoelektra efiko
photoelectric in Basque: Efektu fotoelektriko
photoelectric in Persian: اثر فوتوالکتریک
photoelectric in French: Effet photoélectrique
photoelectric in Galician: Efecto fotoeléctrico
photoelectric in Korean: 광전 효과
photoelectric in Croatian: Fotoelektrični učinak
photoelectric in Indonesian: Efek fotolistrik
photoelectric in Italian: Effetto fotoelettrico
photoelectric in Hebrew: האפקט הפוטואלקטרי
photoelectric in Lithuanian: Fotoefektas
photoelectric in Hungarian: Fényelektromos jelenség
photoelectric in Marathi: प्रकाशीय विद्युत परिणाम
photoelectric in Dutch: Foto-elektrisch effect
photoelectric in Japanese: 光電効果
photoelectric in Norwegian: Fotoelektrisk effekt
photoelectric in Polish: Efekt fotoelektryczny
photoelectric in Portuguese: Efeito fotoeléctrico
photoelectric in Romanian: Efectul fotoelectric
photoelectric in Russian: Фотоэффект
photoelectric in Slovak: Fotoelektrický jav
photoelectric in Slovenian: Fotoelektrični pojav
photoelectric in Serbian: Фотоелектрични ефекат
photoelectric in Finnish: Valosähköinen ilmiö
photoelectric in Swedish: Fotoelektrisk effekt
photoelectric in Tamil: ஒளிமின் விளைவு
photoelectric in Thai: ปรากฏการณ์โฟโตอิเล็กทริก
photoelectric in Vietnamese: Hiệu ứng quang điện
photoelectric in Turkish: Fotoelektrik etki
photoelectric in Ukrainian: Фотоефект
photoelectric in Chinese: 光电效应

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