By combination of which processes,a rainbow is formed?

An electric lamp is fixed at the ceiling of a circular tunnel as shown in the figure. What is the ratio of the intensities of light at base $A$ and a point $B$ on the wall?

During a cloudy day,a primary and a secondary rainbow may be created,then the:

$A$ ray of sunlight enters a spherical water droplet $(n = 4/3)$ at an angle of incidence $53^o$ measured with respect to the normal to the surface. It is reflected from the back surface of the droplet and re-enters into air. The angle between the incoming and outgoing ray is $.......^o$ [Take $\sin \,53^o = 0.8$]

$A$ point source $S$ is placed at a distance of $15 \; cm$ from a converging lens of focal length $10 \; cm$. Where should a concave mirror of focal length $12 \; cm$ be placed so that a real image is formed on the object itself (in $; cm$)?

If the polarising angle of a piece of glass for green light is $54.74^o$,then the angle of minimum deviation for an equilateral prism made of the same glass is......$^o$ (Given $\tan 54.74^o = 1.414$)