In photoelectric effect, if the incident light had a frequency less than a minimum frequency
v0, then no electrons are ejected regardless of the light's amplitude. This minimum frequency is also called the threshold frequency, and the value of
v0 depends on the metal. For frequency greater than
v0, electrons would be ejected from the metal. Furthermore, the kinetic energy of the photoelectrons is proportional to the light frequency (v)
The relationship between photoelectron kinetic energy
T and light frequency
v is shown in graph below
Graph shows that kinetic energy
T is linearly increasing with light frequency (v).
However, for a given photosensitive material and frequency of incident light, number of photoelectrons emitted per second is directly proportional to the intensity of incident light i.e. Number of electrons emitted
∝J.
Also, photoelectric emission is an instantaneous process.