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(A) The intensity $I$ of light at a distance $r$ from a point source is given by $I = \frac{P}{4\pi r^2}$, so $I \propto \frac{1}{r^2}$.When the dista

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the emission of electrons per second will be four times

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(A) The intensity $I$ of light at a distance $r$ from a point source is given by $I = \frac{P}{4\pi r^2}$, so $I \propto \frac{1}{r^2}$.When the distance is changed from $d$ to $\frac{d}{2}$, the new intensity $I'$ becomes $I' = \frac{1}{(d/2)^2} = 4 	imes \frac{1}{d^2} = 4I$.Since the number of photoelectrons emitted per second is directly proportional to the intensity of incident light, the emission rate becomes $4$ times the original value.According to Einstein's photoelectric equation, $KE_{max} = h
u - \phi$, where $
u$ is the frequency of incident light and $\phi$ is the work function.Since the frequency $
u$ remains unchanged, the maximum kinetic energy $(KE_{max})$ and the stopping potential $(V_s)$ remain unchanged, as $eV_s = KE_{max}$.

The distance between a light source and a photoelectric cell is $d$. If the distance is decreased to $\frac{d}{2}$, then:

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The cathode of a photoelectric cell is changed such that the work function changes from $W_1$ to $W_2$ $(W_2 > W_1)$. If the current before and after change are $I_1$ and $I_2$,all other conditions remaining unchanged,then (assuming $h\nu > W_2$):

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