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Question

(C) The intensity $I$ of light from a point source is inversely proportional to the square of the distance $d$ from the source,i.e.,$I \propto 1/d^2$.

Vedclass · Accepted Answer

$4 n$ and $E$

Vedclass · Answer

(C) The intensity $I$ of light from a point source is inversely proportional to the square of the distance $d$ from the source,i.e.,$I \propto 1/d^2$.When the distance is changed from $d$ to $d/2$,the new intensity $I'$ becomes $I' \propto 1/(d/2)^2 = 4/d^2 = 4I$.The rate of emission of photoelectrons is directly proportional to the intensity of incident light. Therefore,the new rate becomes $4n$.The maximum kinetic energy $E$ of the photoelectrons is given by Einstein's photoelectric equation: $E = h
u - \phi$,where $h$ is Planck's constant,$
u$ is the frequency of incident light,and $\phi$ is the work function of the metal.Since the frequency $
u$ of the monochromatic light source remains unchanged,the maximum kinetic energy $E$ remains constant.

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