When light of frequency greater than threshold frequency fall on a metal surface, electrons are emitted out from metal surface this effect is known as photoelectric effect.

Laws of photoelectric effect-

1.    The rate of photoemission is directly proportional to the intensity of incident radiation.

2.    The velocity of emitted photon depends upon frequency of incoming photon.

3.    The energy of emitted electron is independent on intensity of incoming photon.

4.    There is no time lag between incident photon and emission of electron.