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 two crossed polarisers P1 and P2, with a polaroid sheet P3 placed between them.
Let I0 be the intensity of polarised light after passing through the first polariser P1. If θ is the angle between the axes of P1 and P3, then the intensity of the polarised light after passing through P3 will be I=I0cos2θ.
As P1 and P2 are crossed, the angle between the axes of P1 and P2 = 90°.
∴ Angle between the axes of P2 and P3 = (90°−θ)
The intensity of light emerging from P2 will be given by
The intensity of polarised light transmitted from P2 will be maximum when
Also, the maximum transmitted intensity will be given by