An unpolarized beam of intensity $2a^2$ passes through a thin polaroid. Assuming zero absorption in the polaroid,the intensity of emergent plane-polarized light is

What is a polarizer and an analyser?

$A$ source of light is placed in front of a screen. The intensity of light on the screen is $I.$ Two Polaroids $P_{1}$ and $P_{2}$ are placed between the source of light and the screen such that the intensity of light on the screen is $I/2.$ By what angle (in degrees) should $P_{2}$ be rotated so that the intensity of light on the screen becomes $3I/8?$

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 an angle $60^{\circ}$ and $90^{\circ}$ with respect to the axis of $P_1$. The source has an intensity $I_0$. What is the intensity of transmitted light through $P_3$? $\left(\cos 60^{\circ}=0.5, \cos 30^{\circ}=\frac{\sqrt{3}}{2}\right)$

An unpolarized light passes through three polarizing sheets whose polarizing directions make an angle of $30^o$,$60^o$,and $30^o$ with the $y$-axis in the same sense. What fraction of the initial intensity is transmitted by the system?

Define unpolarized light and polarized light.