(a) Define the term 'intensity of radiation' in photon picture.
(b) Plot a graph showing the variation of photo current vs collector potential for three different intensities $$I_1>I_2>I_3,$$ two of which $$(I_1 and I_3)$$ have the same frequency v and the third has frequency v1>v.
(c) Explain the nature of the curves on the basis of Einstein's equation.
(a) The amount of light energy or photon energy incident per metre square per second is called intensity of radiation.
(c) As per Einstein's equation,
(i) The stopping potential is same for $$I_1$$ and $$I_2$$ as they have the same frequency.
(ii) The saturation currents are as shown in figure because $$I_1>I_2>I_3.$$