Question

A photon of energy hv is absorbed by a free electron of a metal with work-function hv − φ.
(a) The electron is sure to come out.
(b) The electron is sure to come out with kinetic energy hv − φ.
(c) Either the electron does not come out or it comes our with kinetic energy hv − φ.
(d) It may come out with kinetic energy less than hv − φ.

Answer 1

(d) It may come out with kinetic energy less than hv − φ.

When light is incident on the metal surface, the photons of light collide with the free electrons. In some cases, a photon can give all the energy to the free electron. If this energy is more then the work-function of the metal,then there are two possibilities. The electron can come out of the metal with kinetic energy hv − φ or it may lose energy on collision with the atoms of the metal and come out with kinetic energy less than hv − φ. Thus, it may come out with kinetic energy less than hv − φ.