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