Question: Q. 10. (i) Define the term ‘intensity’ of radiation in photon picture.
(ii) Plot a graph showing the variation of photo current Vs. collector potential for three different intensities $I_{1}, I_{2}$ and $I_{3}\left(I_{1}>I_{2}>I_{3}\right)$, two of which $\left(I_{1}\right.$ and $I_{2}$ ) have the same frequency $v$ and third has frequency $v_{1}>v$.
(iii) Explain the nature of the curves on the basis of Einstein’s equation.
U] [OD South 2016]
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Solution:
Ans. (i) The amount of light energy / number of photons, incident per metre square per second is called intensity of radiation.
(ii)
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(iii) As per Einstein’s equation
The stopping potential is same for $I_{1}$ and $I_{2}$ as they have same frequency.
The saturation currents are as shown, because
$$ I_{1}>I_{2}>I_{3} $$
