A photoelectric cell is illuminated by a point source of light 1 m away. When the source is shifted to 2 m then (a) each emitted electron carries one quarter of the initial energy (b) number of electrons emitted is half the initial number (c) each emitted electron carries half the initial energy (d) number of electrons emitted is a quarter of the initial number

Answer: (d). Intensity of a point source I ∝ 1/r²; number of photoelectrons ∝ I. r: 1 → 2 m ⇒ I' = I/4. Energy of each electron depends only on frequency, so it is unchanged. So the answer is (d) number of electrons becomes a quarter.

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Photoelectric Experiment: Intensity, Stopping Potential & Graphs

A photoelectric cell is illuminated by a point source of light 1 m away. When the source is shifted to 2 m then

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Answer: (d)

Intensity of a point source $I \propto \frac{1}{r^2}$ ; number of photoelectrons $\propto I$ .
$r: 1 \to 2$ m $\Rightarrow I' = I/4$ .
Energy of each electron depends only on frequency, so it is unchanged.
So the answer is (d) number of electrons becomes a quarter.

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