Disuss the intensity of transmitted light when a polaroid sheet is rotated between two crossed polaroids ?

Explanation

`I_(0)`: intensity of polarised light after passing through the `P_(1)` Intensity of light after passing through `P_(2)`
`I^(')=I_(0) cos^(2) theta`
Intensity of emergent light from `P_(3)`
`I=I^(') cos^(2)(90-theta)=I_(0) cos^(2) theta sin^(2) theta`
`=I_(0)/4(2 sinthetacostheta)^(2)=I_(0)/4(sin2theta)^(2)`
I will be maximum if `sin 2theta=1=sin(pi//2)`
`2theta=pi/2 implies theta=pi/4`