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Polarisation – Malus Law

Two polariods P1 and P2 are placed with their pass axes perpendicular to each other. Unpolarised light of intensity Io is incident on P1. A third polariod P3 is kept between P1 and P2 such that its pass axis makes an angle of 30 with that of P1. Determine the intensity of light transmitted through P1,P2 and P3.

 

Asked Rashmi

Answer

polarisation1

Appply Malus’ Law

The intensity of light from the first polaroid P1 is Io/2

From P3, the intensity is (Io/2) cos230 =(Io/2)(3/4)=3Io/8

 

 

polarisationFrom P2, the intensity is (3Io/8)cos260= (3Io/8)(1/4)= 3Io/32

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