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(B) When unpolarised light of intensity $I_0$ passes through the first polaroid,the intensity of the emergent light is $I_1 = \frac{I_0}{2}$.According

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$\frac{3 I_0}{32}$

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(B) When unpolarised light of intensity $I_0$ passes through the first polaroid,the intensity of the emergent light is $I_1 = \frac{I_0}{2}$.According to Malus' Law,the intensity of light emerging from a polaroid is $I = I_{incident} \cos^2 	heta$,where $	heta$ is the angle between the pass axis of the polaroid and the plane of polarisation of the incident light.For the second polaroid,the angle between its pass axis and the pass axis of the first polaroid is $	heta_1 = 30^{\circ}$. Thus,the intensity of light emerging from the second polaroid is $I_2 = I_1 \cos^2 30^{\circ} = \left(\frac{I_0}{2}ight) \left(\frac{\sqrt{3}}{2}ight)^2 = \left(\frac{I_0}{2}ight) \left(\frac{3}{4}ight) = \frac{3 I_0}{8}$.For the third polaroid,the angle between its pass axis and the pass axis of the second polaroid is $	heta_2 = 90^{\circ} - 30^{\circ} = 60^{\circ}$. Thus,the intensity of light emerging from the third polaroid is $I_3 = I_2 \cos^2 60^{\circ} = \left(\frac{3 I_0}{8}ight) \left(\frac{1}{2}ight)^2 = \left(\frac{3 I_0}{8}ight) \left(\frac{1}{4}ight) = \frac{3 I_0}{32}$.

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