NEET UG 2002 — Optics

For the given incident ray as shown in the figure, the condition of the total internal reflection of this ray and the minimum refractive index of prism will be: 

A bulb is located on a wall. Its image is to be obtained on a parallel with the help of a convex lens. If the distance between parallel walls is ' $d$ ' then the required focal length of the lens placed in between the walls is: