JEE Main · 2022 · 29 Jul 2022 · Shift 2 · Wave Optics

An unpolarised light beam of intensity

2 I_{0}

is passed through a polaroid P and then through another polaroid Q which is oriented in such a way that its passing axis makes an angle of

3 0^{\circ}

relative to that of P. The intensity of the emergent light is

(A) $\frac{I _{0}}{4}$
(B) $\frac{I _{0}}{2}$
(C) $\frac{3 I _{0}}{4}$ ✓ Correct
(D) $\frac{3 I _{0}}{2}$

Answer: (C)

Solution

When unpolarised light of intensity

2 I_{0}

passes through the first polaroid P, the intensity becomes:

I_{1} = \frac{1}{2} (2 I_{0}) = I_{0}

When this polarised light passes through the second polaroid Q at angle

30°

, by Malus's law:

I_{2} = I_{1} cos^{2} 30° = I_{0} \times (\frac{3}{2})^{2} = I_{0} \times \frac{3}{4} = \frac{3 I _{0}}{4}

JEE Main · 2022 · 29 Jul 2022 · Shift 2 · Single correct option

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