Write three experimental observation of photoelectric effect.

Explanation

(1) Photoelectric effect is instantaneous process.
(2) Photoelectric effect does not take place if the frequency of incident radiation is less than threshold frequency.
(3) The strength of photoelectric current is directly proportional to the intensity of incident radiation, provided the frequency of incident radiation is greater than threshold frequency.
(4) The stopping potential or equivalently maximum kinetic energy of the photo electrons is directly proportional to the frequency of incident radiation. It is independent of the intensity of incident radiation.
(5) For given photosensitive material and frequency of incident radiation, saturation current is proportional to intensity of incident radiation. (Any three)