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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

Asked in JEE Main 24th Jan 2nd Shift 2026 · Inverse-square scaling and intensity in a medium

• (1) increase by 8 times
• (2) decrease by 8 times
• (3) increase by 64 times
• (4) decrease by 4 times

Step-by-step solution

Why the other options are wrong

• (1) comes from intensity falls with distance; it cannot increase as the sphere grows
• (2) 8 is the volume factor, not the radius factor squared — r doubles, so I falls by 4
• (3) 64 = 8² treats the volume factor as if it were the radius factor and then squares it

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