Through which characteristic can we distinguish light waves from sound waves?

Two polaroid sheets are placed one over the other with their axes inclined to each other at $30^{\circ}$. The ratio of the intensity of the unpolarised incident light and the polarised emergent light is

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 of $60^{\circ}$ and $90^{\circ}$ with respect to the axis of $P_1$. The source has an intensity $I_0 = 256 \ W/m^2$. Find the intensity of light at point $O$. (in $W/m^2$)

Two Nicols are oriented with their principal planes making an angle of $60^\circ$. The percentage of incident unpolarized light which passes through the system is......$\%$

An unpolarized light beam of intensity $I_0$ is passed through a first polaroid $A$ and then through a second polaroid $B$. If the principal plane of polaroid $B$ makes an angle of $45^{\circ}$ with that of $A$,find the intensity of the emerging light.

In the visible region of the spectrum,the rotation of the plane of polarization is given by $\theta = a + \frac{b}{\lambda^2}$. The optical rotation produced by a particular material is found to be $30^\circ$ per mm at $\lambda = 5000 \ \mathring{A}$ and $50^\circ$ per mm at $\lambda = 4000 \ \mathring{A}$. The value of constant $a$ will be: