JEE Main 2026 Apr 6 Shift 1, Physics Q15: Electromagnetic Waves

JEE Main2026Apr 6, Shift 1Physics

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
$I_{0}$
C
$\frac{I _{0}}{2}$
D
$\frac{I _{0}}{2}$

Solution

For a point source emitting isotropically, intensity depends only on radial distance: $I = \frac{P}{4 π r ^{2}}$ .

The detector is moved along the same sphere (same $r = L$ ), so the intensity is unchanged.

$∴ I_{new} = I_{0}$ .

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JEE Main 2026 Apr 6 Shift 1, Physics Q15: Electromagnetic Waves

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