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

When unpolarised light is passed through crossed polaroids, then light passing through the first polaroid:

$A$ calcite crystal is placed over a dot on a piece of paper and rotated. On seeing through the calcite,one will see:

$A$ polarized light of intensity $I_0$ is passed through another polarizer whose pass axis makes an angle of $60^o$ with the pass axis of the former. What is the intensity of emergent polarized light from the second polarizer?

For light of intensity $I_0$,a polaroid is placed at an angle of $45^\circ$. What will be the intensity of the light passing through the polaroid after polarization?

$A$ beam of unpolarized light passes through a tourmaline crystal $A$ and then it passes through a second tourmaline crystal $B$ oriented so that its principal plane is parallel to that of $A$. The intensity of emergent light is $I_0$. Now $B$ is rotated by $45^{\circ}$ about the ray. The emergent light will have intensity $(\cos 45^{\circ} = \frac{1}{\sqrt{2}})$.