A point source is kept at the center of a spherically enclosed detector. If the volume of the detector increased by 8 times, the intensity will
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A point source is kept at the center of a spherically enclosed detector. If the volume of the detector increased by 8 times, the intensity will

G1 Physics · Accepted Answer

For a spherical detector, V ∝ R³. If the volume becomes 8 times, R'³ = 8R³. Hence, R' = 2R. For a point source, intensity varies inversely as the square of distance: I ∝ 1/R². Therefore, I'/I = R²/R'² = R²/(2R)² = 1/4. Hence the intensity decreases by 4 times. Correct option: D.