Write Einstein's photoelectric equation. State clearly how this equation is obtained using the photon picture of electromagnetic radiation.
Write the three salient features observed in photoelectric effect which can be explained using this equation.

Explanation

`hv =phi_(0) + K_("max")`
Energy (hv), carried by a photon of frequency v, is absorbed (by the electrons on the surface) to :
(a) overcome the work function of metal (`phi_(0)`)
(b) Impart maximum kinetic energy to the emitted electron (`K_("max")`)
`:. hv =phi_(0) + K_("max")`
Three salient features (Any three) :
(i) Cut-off potential of the emitted electrons is proportional to v
(ii) Maximum kinetic energy is independent of the intensity of incident radiations.
(iii) Photoelectric emission of electrons is possible only when `v gt v_(0)`
(iv) Emission of electrons is instantaneous.