Kindly answer the question.



 

Solution
The emission of electrons from the surface of a metal when it is irradiated with a radiation of suitable frequency such as visible light or ultraviolet radiation is known as photoelectric effect. 

This phenomena explains the particle nature of light. Light consists of discrete particles called photons. These photons have a particular energy proportional to the frequency of the light (given by the relation E = hν). 



(ii)

When the photon strikes the surface of the metal, it collides with the electrons and transfers its energy to the electrons. If this energy is equal to or higher than the minimum energy required to remove the electron from the surface of the metal, the electron will be ejected. 

This minimum energy is determined by the threshold frequency. Each metal has its characteristic threshold frequency. 

Therefore if the frequency of the striking photon is less than the threshold frequency of the metal, no electrons would be emitted and hence photoelectric effect will not be observed. It will be observed only when the frequency of the striking photon is equal to or larger than the threshold frequency.