(a) Why photoelectric effect cannot be explained on the basis of wave nature of light?
(b) Write the basic features of photon picture of electromagnetic radiation on which Einstein's photoelectric equation is based.

Explanation

(a) Wave nature of radiation cannot explain the following :
(i) The instaneous ejection of photoelectrons.
(ii) The existence of threshold frequency for a metal surface.
(iii) The fact that kinetic energy of the emitted electrons is independent of the intensity of light and depends upon its frequency.
Thus, the photoelectric effect cannot be explained on the basis of wave nature of light.
(b) Photon picture of electromagnetic radiation on which Einstein's photoelectric equation is based on particle nature of light. Its basic features are :
(i) In interaction with matter, radiation behaves as if it is made up of particles called photons.
(ii) Each photon has energy E = hv and momentam `p = (hv)/(c)` and speed C, the speed of light.
(iii) All photons of light of a particular frequency v, or wavelengh `lambda` have the same energy `E=hv = (hc)/(lambda)` and momentum `p=(hv)/(c) =(h)/(lambda)` whatever the intensity of radiation may be.
(iv) By increasing the intensity of light of given wavelength, there is only an increase in the number of photons per second crossing a given area, with each photon having the same energy. Thus, photon energy is independent of intensity of radiation.
(v) Photons are electrically neutral and are not deflected by electric by electric and magnetic fields.