Question

Two Polaroid's A and B are kept in crossed position. How should a third Polaroid, C be placed between them so that the intensity of polarized light transmitted by Polaroid B reduced to $1/8^{th}$ of the intensity of unpolarised light incident on A.

Answer 1

the third polaroid should be placed in such a way that it should bisect the angle between the two polaroids at an angle of ${45}^0$ from polaroid A the intensity of light coming out of$A=\frac{I}{2}$ Then using Malus Law,

After$C=\frac{l}{2}\times cos2\theta =\frac{l}{2}\times cos2\left(45\right)$

B=$\frac{1}{8}$