Plane light is made up of waves with the same direction of vibration for all of them. Light can be polarised through reflection or passing through filters, such as crystals, that transmit vibration in one plane but not in others.

As shown in figures, three identical polaroids $P_1$, $P_2$ and $P_3$ are placed one after another. The pass axis of $P_2$ and $P_3$ are inclined at angle of $60º$ and $90º$ with respect to axis of $P_1$. The source $S$ has an intensity of $256 \mathrm{W} {\mathrm{m}}^{-2}$. The intensity of light at point $O$ is _____$\mathrm{W} {\mathrm{m}}^{-2}$.

How will you distinguish experimentally between ordinary light and plane-polarized light?

A transparent medium shows relation $i$ and $r$ as shown. If the speed of light in vacuum is $c,$ the Brewster angle for the medium is