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Question 20199
JEE Physics · Hard

Electromagnetic Waves and Wave Optics: EM Wave Intensity and Distance MCQ

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EM Wave Intensity and DistanceHardQuestion 20199

Question

The intensity of EM radiation from a point source varies with distance r as:
  1. A
    1/r
  2. B
    1/r²
    Correct
  3. C
    1/r³
  4. D
    r²

Correct answer

1/r²

Explanation

Energy spreads over a sphere of area 4πr², so intensity I = P/(4πr²) ∝ 1/r². This is the inverse square law for radiation from a point source.

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