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JEE Main 2023 (10 Apr, Shift 1) · Polarisation

Polarisation question from JEE Main 2023 (10 Apr, Shift 1)

Q35JEE Main 2023 · 10 APR · SHIFT 1Medium

Polarisation

Unpolarised light of intensity 32 Wm−2-2 passes through the combination of three polaroids such that the pass axis of the last polaroid is perpendicular to that of the pass axis of first polaroid. If intensity of emerging light is 3 Wm −2-2, then the angle between pass axis of first two polaroids is ______________ ∘{}^\circ.

Numerical answer type. Work it out, then open the answer.

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Answer: 30

  1. Last crossed with first: I=I02cos⁡2θsin⁡2θ=I08sin⁡22θI = \frac{I_0}{2}\cos^2\theta\sin^2\theta = \frac{I_0}{8}\sin^2 2\theta
  2. 3=328sin⁡22θ⇒sin⁡22θ=34⇒2θ=60∘3 = \frac{32}{8}\sin^2 2\theta \Rightarrow \sin^2 2\theta = \frac{3}{4} \Rightarrow 2\theta = 60^\circ
  3. So θ=30∘\theta = 30^\circ.
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