CUET · PHYSICS · PYQ PAPER 2025
A photosensitive surface 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 eighth of the initial energy.
- B number of emitted electrons is half the initial number
- C each emitted electron carries half the initial energy
- D number of emitted electrons is a quarter of the initial number
Answer & Solution
Correct Answer
(D) number of emitted electrons is a quarter of the initial number
Step-by-step Solution
Detailed explanation
Intensity \( I \propto \frac{1}{r^2} \) Initial intensity \( I_1 \propto \frac{1}{1^2} \) Final intensity \( I_2 \propto \frac{1}{2^2} \) \( \frac{I_2}{I_1} = \frac{1/2^2}{1/1^2} = \frac{1}{4} \) Number of emitted electrons \( N \propto I \) So, \( N_2 = \frac{1}{4} N_1 \)
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