Q13 of 26 Page 1

(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 I1>I2>I3, two of which (I1 and I2) have the same frequency n and the third has frequency n1>n.
(c) Explain the nature of the curves on the basis of Einsteins equation.

(a) The intensity of radiation is defined as the number of photons incident, per unit surface area per unit time.

(b) The photocurrent curve is given as follows:


(c) Here, curves (1) and (2) have the same frequency and hence the same stopping potential. But the number of photons striking the metal surface or the intensity of (1) is greater than (2). Hence, the number of photoelectrons produced is more for (1) than (2).


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