Explain why photoelectric effect cannot be explained on the basis of wave nature of light.

Explanation

(i) When light is incident on the target, there is a continuous supply of energy to the electrons.
(ii) According to wave theory, light of greater intensity should impart greaterkinetic energy to the liberated electrons ( Here, intensity of light is the energy delivered per unit area per unit time ).
But this does not happen. The experiments show that maximum kinetic energy of the photoelectrons does not depend on the intensity of the incident light.
(iii) According to wave theory, if a sufficiently intense beam of light is incident on the surface, electrons will be liberated from the surface of the target, however low the frequency of the radiation is.
From the experiments , we known that photoelectric emission is not possible below a certain minimum frequency. Therefore, the wave theory fails to explain the existence of threshold frequency.
(iv) SInce the energy of light is spread across the wavefront, the electrons which receive energy from it are large in number. Each electron needs considerable amount of time ( a few hours) to get energy sufficient to overcome the work frunction and to get liberated from the surface.
But experiment show that photoelectric emission is almost instantaneous process ( the time lag is less than `10^(-9)` s after the surface is illuminated ) which could not be explained by wave theory.
Thus, the experimental observations of photoelectric emission could not be explained on the basis of the wave theory of light.