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A point light source emits E.M. waves in free space. A detector, placed at a distance of L m, measures the intensity as I₀. The detector is now shifted to another location on the same spherical surface ensuring the angle between original location and new location as 45°. The measured intensity at new location will be ______.

Asked in JEE Main 6th April 1st Shift 2026 · Wavefronts and Huygens construction

• (1) (I₀)/4
• (2) I₀
• (3) (I₀)/(√2)
• (4) (I₀)/2

Step-by-step solution

Why the other options are wrong

• (1) Applies an inverse-square drop as if the distance had doubled, though the detector stays at distance L.
• (3) Multiplies by cos 45° as if the field amplitude projected onto the new direction.
• (4) Applies Malus's law cos² 45° though no polarizer is involved.

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