Out of the following statements,which is not correct?

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

Statement-$I$: On viewing the clear blue portion of the sky through a calcite crystal,the intensity of transmitted light varies as the crystal is rotated.
Statement-$II$: The light coming from the sky is polarized due to the scattering of sunlight by particles in the atmosphere. The scattering is largest for blue light.

When unpolarized light of intensity $I_0$ is incident on a polarizer,what will be the intensity of the light that does not pass through it?

$A$ 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 $(\cos 45^{\circ} = \frac{1}{\sqrt{2}})$.

An unpolarised beam of light of intensity $I_0$ passes through two linear polarisers making an angle of $30^{\circ}$ with respect to each other. The emergent beam will have an intensity: