An unpolarised light of intensity 64 Wm^(-2) passes through three polarisers such that the transmission axis of the last polariser is normal to first. If the intensity of emerging light is 6 Wm(-2),then angle between first two polariser may be

Options

A. `60^(@)`
B. `45^(@)`
C. `90^(@)`
D. `120^(@)`

Answer

A

Explanation

`I_(2)=I_(1)cos^(2)(90^(@)-theta)=(I')/2cos^(2)thetasin^(2)theta=(I')/8(sin2theta)^(2)`

`3=32/8(sin 2theta)^(2)`
`sin 2theta=sqrt(3)/2=sin 60^(@)or sin 120^(@)`
`theta=30^(@)or 60^(@)`