The experimentally observed facts of photoelectric effect can be explained the help of Einstein's photoelectric equation.
 |
| Photo-electric Effect |
i) Each incident photon liberates one electron, then the increase of intensity of the light (the number of photons per unit area per unit time) increases the number of electrons emitted thereby increasing the photo-current, The same has been experimentally observed.
ii) From K(max)=h v—Φ•, it is evident max that K is proportional to the frequency max of the incident light and is independent of intensity of the light.
iii) There must be minimum energy (equal to the work function of the metal) for incident photons to liberate electrons from the metal surface. ( h v= h v 1/2 m v^2 ).
Below this value of energy, emission of electrons is not possible. Correspondingly, there exists minimum frequency called threshold frequency below which there is no photoelectric emission.
iv) According to quantum concept, the transfer of photon energy to the electrons is instantaneous so that there is no time lag between incidence of photons and ejection of electrons. Thus, the photoelectric effect is explained on the basis of quantum concept of light.
Laws of Photoelectric Effect :
i) For a given metallic surface, the emission of photo-electrons takes place only if the frequency of incident light is greater than a certain minimum frequency called the threshold frequency.
 |
| Photo-electric Effect |
ii) For a given frequency of incident light above threshold value, the number of photo-electrons emitted is directly proportional to the intensity of the incident light. The saturation current is also directly proportional to the intensity of incident light.
iii) Maximum kinetic energy of the photo electrons is independent of intensity of the incident light.
iv) Maximum kinetic energy of the photo electrons from a given metal is directly proportional to the frequency of incident light.
v) There is no time lag between incidence of light and ejection of photo-electrons.
" When you change the way you look at things, the things you look at change. " --- Max Planck.---
