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Concepts Of Physics MCQ Edition [Volume 1]PhysicsLight Waves

The inverse square law of intensity (where intensity 1 r^2 ) holds true for a

Options

  1. Acylindrical source
  2. Bpoint source
  3. Cplane source
  4. Dline source

Correct answer

B. point source

Step-by-step solution

For a point source, the power P is distributed uniformly over a spherical surface of radius r . The surface area of the sphere is A = 4 r^2 . Intensity I = P A = P 4 r^2 . Thus, I 1 r^2 , which is the inverse square law. For a line or cylindrical source, the power is distributed over a cylindrical surface, so I 1 r . For a plane source, the intensity is independent of distance.

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