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# In a photocell experiment, a convex lens is used to focus the light beam. Current strength is I. If the lens is replaced by another lens of half diameter, but same focal length, photoelectric current will be

$\begin {array} {1 1} (a)\;\large\frac{1}{2} & \quad (b)\;\large\frac{1}{4} \\ (c)\;\large\frac{1}{8} & \quad (d)\;\large\frac{1}{16} \end {array}$

Ans : (b)
Since, light gathering power, i.e, intensity is reduced by a
factor of 4 on making the diameter half, and intensity of incident light
is proportional to the photoelectric current.

edited Mar 13, 2014