When light is shone on the surface of an object (usually a metal), the energy of the light is transferred to the electrons in the metal, and the electrons in the metal gain kinetic energy. If the energy of these electrons is greater than the work function of the metal, the electrons are emitted to the outside. This phenomenon is called the external photoelectric effect (or simply the photoelectric effect) or photoemission. The electrons emitted in this case are called photoelectrons. For the external photoelectric effect to occur, the following condition must be met: mv 2 /2 = h ν - W > 0, where v is the speed of the photoelectron. Here, m is the mass of the photoelectron, h is Planck's constant, ν is the frequency of the incident light, and W is the work function of the metal. This relationship is known as Einstein's equation. Various phototubes and camera tubes are electron tubes that utilize this effect. Source: Encyclopaedia Britannica Concise Encyclopedia About Encyclopaedia Britannica Concise Encyclopedia Information |
光が物体 (多くの場合金属) の表面に照射されると,光のエネルギーが金属内電子に与えられ,金属内電子は運動エネルギーを得る。もしこの電子のエネルギーが金属物質の仕事関数より大きいとき,電子は外部に放出される。このような現象を外部光電効果 (単に光電効果ともいう) または光電子放出 photo-emissionという。このとき放出された電子を光電子と呼ぶ。外部光電効果が生じるためには,光電子の速度を v とすると mv2/2=hν-W>0 という条件が成立する必要がある。ここに m は光電子の質量,h はプランク定数,ν は入射光の振動数,W は金属物質の仕事関数である。この関係はアインシュタインの関係式として知られている。各種の光電管,撮像管などは,この効果を利用した電子管である。
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