Two polarizers are placed at crossed position (i.e. having an angle of 90 between them ), a third polarizer making an angle  with the first one is placed between them. An unpolarized light of intensity I0 is incident on the first oneand passes through all the three polarizers. Find the light intensity of the emergent beam.

Asked by Abhineet | 26th Nov, 2019, 02:04: AM

Expert Answer:

If incident intensity is Io on first polariser, intensity of light transmitted by first polariser is ( Io /2 ) .
 
If polariser P2 makes an pass angle θ with P1 , then by Malus law, transmitted intensity by P2 = ( Io /2 ) Cos2θ
 
Since P1 and P3 are having pass angles perpendicular to each other, pass angle of P3 with respect to P2 = 90 - θ
 
Hence transmitted intensity by P3 = ( Io /2 ) Cos2θ Cos2(90-θ) = ( Io /2 ) Cos2θ Sin2θ

Answered by Thiyagarajan K | 26th Nov, 2019, 08:39: AM