Three identical polaroids P_1, P_2 and P_3 ar | vedclass

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Question

(A) Let the initial intensity of unpolarized light be $I_0 = 256 \ W/m^2$.When unpolarized light passes through the first polaroid $P_1$,the intensity

Vedclass · Accepted Answer

$24$

Vedclass · Answer

(A) Let the initial intensity of unpolarized light be $I_0 = 256 \ W/m^2$.When unpolarized light passes through the first polaroid $P_1$,the intensity of the transmitted light becomes $I_1 = I_0 / 2 = 256 / 2 = 128 \ W/m^2$.The pass axis of $P_2$ is at an angle $	heta_1 = 60^{\circ}$ with respect to $P_1$. According to Malus' Law,the intensity after $P_2$ is $I_2 = I_1 \cos^2(	heta_1) = 128 	imes \cos^2(60^{\circ}) = 128 	imes (0.5)^2 = 128 	imes 0.25 = 32 \ W/m^2$.The pass axis of $P_3$ is at an angle of $90^{\circ}$ with respect to $P_1$. The angle between the pass axes of $P_2$ and $P_3$ is $	heta_2 = 90^{\circ} - 60^{\circ} = 30^{\circ}$.Applying Malus' Law again for $P_3$,the final intensity at point $O$ is $I_3 = I_2 \cos^2(	heta_2) = 32 	imes \cos^2(30^{\circ}) = 32 	imes (\sqrt{3}/2)^2 = 32 	imes (3/4) = 24 \ W/m^2$.

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