Optics Questions

A beam of unpolarised light of intensity $I_0$ is passed through a polaroid $A$ and then through another polaroid $B$ which is oriented so that its principal plane makes an angle of $45^{\circ }$ relative to that of $A$. The intensity of the emergent light is:

Two coherent point sources $S_1$ and $S_2$ are separated by a small distance $d$ as shown. The fringes obtained on the screen will be:

The graph between angle of deviation ($\delta$) and angle of incidence ($i$) for a triangular prism is represented by:

Diameter of plano-convex lens is $6\text{cm}$ and thickness at the centre is $3\text{mm}$. If speed of light in material of lens is $2\times 10^8\text{m/s}$, the focal length of the lens is: