Two polaroids are placed in the path of unpolarised beam of intensity ' I₀ ' such that no light is emitted from the second polaroid. If a third polaroid whose polarisation axis makes an angle ' θ ' with the polarisation axis of first polaroid is placed between these polaroids then the intensity of light emerging from the last polaroid will be (a) I₀/4(sin 2θ)² (b) I₀/8(sin 2θ)² (c) I₀/4sin ²θ (d) I₀/8sin ²θ

Answer: (b). No output means the two polaroids are crossed ( 90°). The middle one is at θ to the first and 90° - θ to the last. I = I₀/2cos ²θcos ²(90° - θ) = I₀/2cos ²θsin ²θ = I₀/8(sin 2θ)² So the answer is (b).

Two polaroids are placed in the path of unpolarised beam of intensity… | MHT CET 2025 (22 Apr, Shift 2)

Q18MHT CET 2025 · 22 APR · SHIFT 2Medium

Polarisation

Two polaroids are placed in the path of unpolarised beam of intensity ' $I_0$ ' such that no light is emitted from the second polaroid. If a third polaroid whose polarisation axis makes an angle ' $\theta$ ' with the polarisation axis of first polaroid is placed between these polaroids then the intensity of light emerging from the last polaroid will be

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Answer: (b)

No output means the two polaroids are crossed ( $90^\circ$ ).
The middle one is at $\theta$ to the first and $90^\circ - \theta$ to the last.
$I = \frac{I_0}{2}\cos^2\theta\cos^2(90^\circ - \theta) = \frac{I_0}{2}\cos^2\theta\sin^2\theta = \frac{I_0}{8}(\sin 2\theta)^2$
So the answer is (b).

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Polarisation question from MHT CET 2025 (22 Apr, Shift 2)

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