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

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Increase by a factor of $4$.

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(B) The intensity of light $I$ is inversely proportional to the square of the distance $d$ from the source,i.e.,$I \propto 1/d^2$.Since the number of photoelectrons emitted per unit time $(dn/dt)$ is directly proportional to the intensity of incident light,we have $(dn/dt) \propto 1/d^2$.Let $d_1 = 1 \ m$ and $d_2 = 1/2 \ m$.The ratio of the number of electrons emitted is given by:$\frac{(dn/dt)_2}{(dn/dt)_1} = \frac{d_1^2}{d_2^2} = \frac{1^2}{(1/2)^2} = \frac{1}{1/4} = 4$.Therefore,the number of emitted electrons increases by a factor of $4$.

$A$ photocell is illuminated by a small source of light placed at a distance of $1 \ m$. When the same source of light is placed at a distance of $1/2 \ m$,the number of electrons emitted by the photocathode will .......

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