Two polariods P1 and P2 are placed with their pass axes perpendicular to each other. Unpolarised light of intensity I_{o }is incident on P1. A third polaroid P3 is kept in between P1 and P2 such that its pass axis makes an angle 45^{0 }with that of P1. determine the intensity of light transmitted though P1, P2 and P3.

_{1}, the intensity of light become I

_{1}= I

_{o}/2

As angle between P

_{1 }and P

_{3}is 45

^{o}, so after passing through it intensity become

${I}_{3}={I}_{1}{\mathrm{cos}}^{2}\vartheta =\frac{{I}_{o}}{2}{\mathrm{cos}}^{2}45=\frac{{I}_{o}}{4}$

Now the angle between P

_{3 }and P

_{2}is 45

^{o}, so after passing through it intensity become

${I}_{2}={I}_{3}{\mathrm{cos}}^{2}\theta =\frac{{I}_{o}}{4}{\mathrm{cos}}^{2}45=\frac{{I}_{o}}{8}$

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