JEE Main 2026 — Jan 24, Shift 2 — Physics solution

JEE Main2026Jan 24, Shift 2Physics

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

Solution

Volume scales as $R^{3}$ . So $V \to 8 V$ means $R \to 2 R$ .

Intensity from a point source $= \frac{P}{4 π R ^{2}}$ , which scales as $1/ R^{2}$ .

$R \to 2 R \Rightarrow$ area scales by 4, so intensity $\to \frac{I _{0}}{4}$ (decreases by a factor of 4).

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