Which of the following statements indicates that light waves are transverse?

Two polaroids $A$ and $B$ are placed in such a way that the pass-axes of the polaroids are perpendicular to each other. Now, another polaroid $C$ is placed between $A$ and $B$, bisecting the angle between them. If the intensity of unpolarised light is $I_0$, then the intensity of the transmitted light after passing through polaroid $B$ will be:

Unpolarised light from air is incident on the surface of a transparent medium of refractive index $1.414$ such that the reflected light is completely polarised. Match the angles given in List-$I$ with the corresponding values given in List-$II$.

$A$. Angle of reflection	$(i)$ $2 \sin^{-1} \left(\sqrt{\frac{2}{3}}\right)$
$B$. Angle of refraction	$(ii)$ $\sin^{-1} \left(\sqrt{\frac{2}{3}}\right) - \sin^{-1} \left(\frac{1}{\sqrt{3}}\right)$
$C$. Angle between incident and completely polarised light	$(iii)$ $\sin^{-1} \left(\frac{1}{\sqrt{3}}\right)$
$D$. Angle of deviation of the incident ray	$(iv)$ $\cos^{-1} \left(\frac{1}{\sqrt{3}}\right)$

What is partially polarised light?

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.

An unpolarised light beam of intensity $2 I_{0}$ is passed through a polaroid $P$ and then through another polaroid $Q$ which is oriented in such a way that its passing axis makes an angle of $30^{\circ}$ relative to that of $P$. The intensity of the emergent light is.