Unpolarised light of intensity `32 Wm^(-2)` passes through three polarizer such that the transmission axis of the last polarizer is crossed with that of the first. The intensity of final emerging light is `3Wm^(-2)`. The intensity of light transmitted by first polarizer will be

Options

A. `32Wm^(-2)`
B. `16Wm^(-2)`
C. `8Wm^(-2)`
D. `4Wm^(-2)`

Answer

B

Explanation

Intensity of polarised light transmitted from 1st polariser,
`I_(1)=I_(0)cos^(2)theta`
but `(cos^(2)theta)_(av)=1/2`
So `I_(1)=1/2I_(0)=32/2=16Wm^(-2)`