Write three characteristic features in photoelectric effect

Write three characteristic features in photoelectric effect which cannot be explained on the basis of wave theory of light, but can be explained only using Einstein’s equation. [Delhi I, II, III 2016]

Three characteristic features of photoelectric effect which can be explained using Einstein’s Equation are as follows.
(i) For a given metal and frequency of incident radiation, the number of photoelectrons ejected per second is directly proportional to the intensity of incident radiation.
(ii) Maximum kinetic energy of the emitted photo electron is independent of the intensity of incident radiations.
(iii) Emission of photoelectrons is instantaneous