Plot a graph showing variation of stopping potential `(V_(0))` with the frequency (v) of the incident radiation for a given photosensitive material. Hence, state the significance of the threshold frequency in photoelectric emission.
Using the principle of energy conservation, write the equation relating the energy of incident photon, threshold frequency and the maximum kinetic energy of the emitted photoelectrons.

Explanation

A graph showing variation of stopping potential `V_(0)` with the frequency v of the incident radiation for a given photosensitive material is shown in figure.
Threshold frequency is the minimum frequency of incident radiation for a given photosensitive surface for causing potoelectric emission. if frequency of incident radiation is less than the threshold frequency, no photo electric emission takes place irrespective of the intensity of incident radiation. let a photon of energy E=hv is incident on a photosensitive material of work function `phi_(0)=hv_(0)` with kinetic energy of photoelectron `K_(max)`. then in accordance with the law of conservation of energy :
`E=phi_(0)+K_(max)`
`implies hv=hv_(0)+K_(max) or h(v-v_(0))=K_(max)`