Q.

Two polarisers P1 and P2 are placed in such a way that the intensity of the transmitted light will be zero. A third polariser P3 is inserted in between P1 and P2, at the particular angle between P2 and P3. The transmitted intensity of the light passing through all three polarisers is maximum. The angle between the polarisers P2 and P3 is:          [2025]

1 π4  
2 π6  
3 π8  
4 π3  

Ans.

(1)

Through P2I1=I0 sin2(π2θ)

I1=I0 cos2θ

Through P3Inet=(I0 cos2θ)sin2θ

Inet=I04 [sin(2θ)]2 for max, Inet θ=45°

So angle between P2 and P3 is π4