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Question 20238
JEE Physics · Hard

Electromagnetic Waves and Wave Optics: Three Polaroids MCQ

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Three PolaroidsHardQuestion 20238

Question

Unpolarised light of intensity I₀ passes through a polariser, then a polaroid at 45°, then one at 90° to the first. Final intensity is:
  1. A
    0
  2. B
    I₀/4
  3. C
    I₀/8
    Correct
  4. D
    I₀/16

Correct answer

I₀/8

Explanation

Step 1: after polariser → I₀/2. Step 2: Malus at 45° → (I₀/2)cos²45° = (I₀/2)(1/2) = I₀/4. Step 3: at 90° to polariser (= 45° to middle polaroid) → (I₀/4)cos²45° = (I₀/4)(1/2) = I₀/8.

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