Question

When unpolarized light is passed through a polarizer, its intensity ______.

Options

• Increases

• Decreases

• Remain unchanged

• Depends on the orientation of the polarize

Answer 1

When unpolarized light is passed through a polarizer, its intensity decreases.

Explanation:

According to Malu’s law,

`I = I_0 cos^2 (theta)`

Here `theta` is the angle between the axes of polarizers and `I_0` is the falling intensity. 

So when unpolarized light passes through a polarizer, the intensity is reduced by a factor of `1/2`. The average `cos^2 theta`, averaged over all angles `theta` is `1/2`.

`I = I_0 <<cos^2 (theta)>>_("allangles")`

= `1/2 I_0`