Two polaroids are placed at `90^(@)` to eachother and the transmitted intensity is zero. What happens when one more polaroid is placed between these two, bisecuting the angle between them. How will the intensity of transmitted light vary on further rotating the third polaroid ?

Explanation

If `I_(0)` is intensity of polarised light from 1st polaroid, then intensity of light transmitted from 3rd polaroid placed in between (for `theta = 45^(@)`) is
`I_(1) = I_(0)cos^(2)theta = I_(0) (cos45^(@))^(2) = (I_(0))/(2)`
Intensity of polarised light from 2nd polaroid already there
`I_(2) = I_(1) cos^(2) 45^(@) = (I_(0))/(2) xx ((1)/(sqrt(2)))^(2) = (I_(0))/(4)`