Question

Unpolarised light with an intensity of $I_{0}=16\, w / m ^{2}$ is incident on a pair of polarisers. The first polariser has its transmission axis aligned at $50^{\circ}$ from the vertical. The second polariser has its transmission aligned at $20^{\circ}$ from the vertical. What is the intensity (in $W/m$) of the light. When it emerges from the second polarizer.

Answer 1

When unpolarised light emerges from $1^{\text {st }}$ polarizer the light is having intensity
$I _{1}=\frac{ I _{0}}{2}=8\, w / m ^{2}$
When it emerges from $2^{\text {nd }}$ polarizer
$I _{2}= I _{1} \cos ^{2} 30^{\circ}$
$=(8)\left(\frac{\sqrt{3}}{2}\right)^{2}=8 \times \frac{3}{4}$
$=6\, w / m ^{2}$