What is a Polaroid ?  Explain it's working in detail.

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 clear sheet of Polaroid is placed on top of a similar sheet so that their axes make an angle of ${\sin }^{-1}\left(\frac{4}{5}\right)$ with each other. The ratio of the intensity of the emergent light to that of polarised light is

A mixture of plane polarised and unpolarised light falls normally on a polarising sheet. On rotating the polarising sheet about the direction of the incident beam, the transmitted intensity varies by a factor of $3$. The ratio of intensities $I_{\mathrm{p}}$ and $I_0$ of the polarised and unpolarised components in the incident beam is

An unpolarised beam of intensity $I_0$ is incident on a pair of nicol prisms making an angle of $60°$ with each other. The intensity of light emerging from the pair is -