If a polaroid is kept in the path of uniformly unpolarised light,the ratio of the intensity of the transmitted light to the intensity of the light when the polaroid was not kept in its path is:

Indicate the signals used for unpolarised,polarised,and partially polarised light.

The tourmaline crystal:

Two polarisers $P_1$ and $P_2$ are placed such that the intensity of the transmitted light is zero. $A$ third polariser $P_3$ is inserted between $P_1$ and $P_2$. If the transmitted intensity of the light passing through all three polarisers is maximum,what is the angle between the polarisers $P_2$ and $P_3$?

$A$ polarized light of intensity $I_{0}$ is passed through another polarizer whose pass axis makes an angle of $60^{\circ}$ with the pass axis of the former. What is the intensity of emergent polarized light from the second polarizer?

Two polaroids are placed in the path of an unpolarised light beam of intensity $I_0$ such that no light is emitted from the second polaroid. If a third polaroid,whose polarisation axis makes an angle $\theta$ with that of the first polaroid,is placed between the polaroids,then the intensity of light emerging from the last polaroid is