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 30 ° relative to

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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 30 ° relative to that of P . The intensity of the emergent light is

TestHub · Accepted Answer

When unpolarized light passes from Polaroid, then it becomes polarised light and intensity becomes half of the original, therefore, $I_{1} = \frac{2 I_{0}}{2} = I_{0}$ .
Given here, $θ = 30 °$ .
Using law of Malus for the second polariser, $I = I_{0} \cos^{2} θ$
We have, intensity of emergent light, $I_{2} = I_{1} \cos^{2} 30 °$
$= I_{0} \frac{3}{4} = \frac{3 I_{0}}{4}$

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