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Concepts Of Physics MCQ Edition [Volume 1]PhysicsLight Waves

A long narrow horizontal slit is placed 1 mm above a horizontal plane mirror. The interference pattern formed by the light arriving directly from the slit and the light arriving after reflection is viewed on a screen placed 1.0 m away from the slit. If the mirror reflects exactly 64 % of the incident light energy, determine the ratio of the maximum intensity to the minimum intensity in the observed interference patte

Options

  1. A9 : 1
  2. B41 : 9
  3. C81 : 1
  4. D16 : 1

Correct answer

C. 81 : 1

Step-by-step solution

Let the intensity of the light arriving directly from the slit be I₁ = I . Since the mirror reflects 64 % of the incident light energy, the intensity of the light arriving after reflection is I₂ = 0.64 I . The maximum intensity in the interference pattern is given by I_ max = ( I₁ + I₂ )^2 . The minimum intensity in the interference pattern is given by I_ min = ( I₁ - I₂ )^2 . The ratio of the maximum intensity to the minimum intensity is: I_ max I_ min = ( I₁ + I₂ I₁ - I₂ )^2 Substituting the values of I₁ and I₂ :

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