Consider the following statements $A$ and $B$ and identify the correct answer:
$A$. Polarised light can be used to study the helical surface of nucleic acids.
$B$. Optical axis is a direction and not any particular line in the crystal.

Unpolarized light of intensity $32 \ W m^{-2}$ passes through three polarizers such that the transmission axes of the first and second polarizers make an angle of $30^\circ$ with each other,and the transmission axis of the last polarizer is crossed with that of the first. The intensity of the final emerging light will be.......$W m^{-2}$

Plane polarised light is passed through a polaroid. On viewing through the polaroid,we find that when the polaroid is given one complete rotation about the direction of the light,one of the following is observed:

The wave property of electrons implies that they will show diffraction effects. Davisson and Germer demonstrated this by diffracting electrons from crystals. The law governing the diffraction from a crystal is obtained by requiring that electron waves reflected from the planes of atoms in a crystal interfere constructively. Which of the following phenomena establishes the transverse nature of light?

As shown in the figure,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 angles of $60^{\circ}$ and $90^{\circ}$ with respect to the axis of $P_1$. The source $S$ has an intensity of $256 \text{ W/m}^2$. The intensity of light at point $O$ is $........... \text{ W/m}^2$.

$A$ polaroid $(I)$ is placed in front of a monochromatic source. Another polaroid $(II)$ is placed in front of this polaroid $(I)$ and rotated until no light passes. $A$ third polaroid $(III)$ is now placed in between $(I)$ and $(II)$. In this case,will light emerge from $(II)$? Explain.