Failure of Electromagnetic Wave Theory To Describe Photoelectric Effect

According to electromagnetic theory, light is a resultant propagation of electric and magnetic field mutually perpendicular to it and it exert force on an electron continuously. But these rigorous theory of light fail to explain the characteristic of photoelectron emitting

from certain metal surface when a light of certain frequency incident on it.

              

       The failure of e.m theory to describing photoelectric effect are given below –

1.      According to e.m theory, light of higher intensity consisting of stronger field and they may liberate electron from the metal surface. So the kinetic energy of the electron i.e. the velocity of emitted photoelectron must depend on the intensity of light not on the frequency of light.

2.      Classically if the intensity of light is very week then the photoelectron will take longer time to come out from the metal surface. Thus there is no reason why photocurrent only depend on intensity of light.

3.      Expt. shows that the photoelectron will not effuse if the frequency is not greater than the threshold frequency. But e.m theory told us that the electron will emitted for any frequency if they given sufficient time to gain energy.

4.      According to e.m theory time requirement of light incident on metal surface then energy taken by the electron and finally to came out from metal surface is quite high than the experimental shown time.


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