Find an expression for intensity of transmitted light when a polaroid sheet is rotated between two crossed polaroids. In which position of the polaroid sheet will the transmitted intensity be maximum?

Let us consider three polaroids A, B and C where C is kept in between A and B.



Using Malu’s Law, the intensity of light emerging from the middle polaroid C is given by,


Therefore, intensity  falls on the polaroid at the end (polaroid B) whose polarisation axis makes an angle of ( 90° - θ ) with the polarisation axis of the angle of middle polaroid.

Therefore, Intensity of light emerging from Polaroid B is, 

  

That is, transmitted intensity will be maximum when sin 2  = 1