The photoelectric effect

The photoelectric effect is the emission of electrons by a material, generally metallic when it is exposed to light or radiationeffet sufficiently high frequency electromagnetic, that depends on the material.
In the photoelectric effect, It sheds light on a metal plate and it emits electrons.
Experimental findings of the photoelectric emission

  • Electrons are issued only if the frequency of the light is sufficiently high and exceeds a limit called threshold frequency frequency
  • This threshold frequency depends on the material and is directly related to the binding energy of the electrons that can be issued
  • The number of electrons emitted in the exposure to light, determines the intensity of electric current, is proportional to the intensity of the light source
  • The kinetic energy of the emitted electrons depends linearly on the frequency of the incident light
  • The photoelectric emission occurs within one less than extremely small 10-9 s after lighting, What makes the almost instantaneous phenomenon.

Interpretation and explanation

This effect cannot be explained satisfactorily when considering that light is a wave, the theory accepted at the time, which helps to explain most of the phenomena in which the light is involved, such optics, and that was translated mathematically by the theory of James Clerk Maxwell.

Indeed, When considering light as a wave, by increasing its intensity and waiting long enough, We should be able to provide enough energy to the material to release electrons. Experience shows that the light intensity is not the only parameter, and that the transfer of energy causing the release of electrons can be done only from a certain frequency.

The photoelectric effect, the incident electromagnetic wave eject electrons from the material.

The interpretation of Einstein, the absorption of a photon, allowed to explain fully all the features of this phenomenon. Photons of light source have a characteristic energy determined by the frequency of the light. When an electron of the material absorbs a photon and the energy of it is sufficient, the electron is ejected ; otherwise the electron cannot escape from the material. As increase the intensity of the light source does not change the energy of the photons, but only their number, It is easy to understand that the energy of the electrons emitted by the material is not the intensity of the light source.

The photoelectric effect dominates at low energies, but the cross section is growing rapidly with the atomic number Z where n ranges from 4 to 5.

Energies and atomic numbers where this process is important, the emitted electron is absorbed over a very short distance such that all its energy is stored in the detector. The x-rays that are emitted in the re