. Photoelectric effect is the phenomenon in which

(a)photons come out of a metal when it is hit by the beam of electrons

(b)photons come out of the nucleus of an atom under the action of an electric field

(c)electrons come out of a metal with a constant velocity which depends upon the frequency and intensity of the incident light wave

(d)electrons come out of metal with different velocities not greater than a certain value which depends only on the frequency of the incident light wave and not on its intensity.