JEE Main · 2026 · 06 Apr 2026 · Shift 1 · EM Waves

A point light source emits E.M. waves in free space. A detector, placed at a distance of L m, measures the intensity as

I_{0}

. The detector is now shifted to another location on the same spherical surface ensuring the angle between original location and new location as

4 5^{\circ}

. The measured intensity at new location will be

____

(A) $\frac{I _{0}}{4}$
(B) $I_{0}$ ✓ Correct
(C) $\frac{I _{0}}{2}$
(D) $\frac{I _{0}}{2}$

Answer: (B)

Solution

For a point source the intensity depends only on distance from the source,

I = \frac{P}{4 π R ^{2}}

. Shifting the detector to another point of the same sphere keeps

R

unchanged, whatever the angular displacement. The intensity at the new location is still

I_{0}

JEE Main · 2026 · 06 Apr 2026 · Shift 1 · Single correct option

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