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In a photoelectric effect experiment, a point source of light illuminates a metal surface. If the source is moved farther away from the metal, what happens to the stopping potential?
- It increases.
- It decreases.
- It remains constant.
- It may either increase or decrease depending on the metal.
Correct answer: It remains constant.
Solution
The stopping potential equals eVₛ = h*f - phi, where f is the frequency of incident light and phi is the work function. Neither f nor phi changes when the source is moved farther away — only the intensity (rate of emission of photoelectrons) decreases. Hence the stopping potential remains constant.
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