Light from sodium lamp is made to pass through two polaroid placed one after the other in the path of light. Taking the intensity of the incident light as `100%`, the intensity of the out coming light that can be varied in the range

Options

A. `0% " to " 100%`
B. `0% " to " 50%`
C. `0% " to " 25%`
D. `0% " to " 75%`

Answer

B

Explanation

Let `I_(0)` be the intensity of incident light. As the light coming from sodium lamp is unpolarised, so the intensity of light emerging from the first polaroid is
`I_(1)=(I_(0))/(2)`
If `theta` is the angle between two polaroids, then the intensity of light emerging from the second polaroid is
`I_(2)=I_(2)"cos"^(2)theta=(I_(0))/(2)cos^(2)theta`
But `I_(0)=100%` (given)
` :. I_(2)=50%"cos"^(2)theta`
Since `theta` varies from `90^(@)` to `0^(@)`, so the intensity of the out coming light can be varied from `0%` to `50%`.