A lens is made up of 3 different transparent media as shown in figure. A point object O is placed on its axis beyond $$2f$$. How many real images will be obtained on the other side?

$$\epsilon_0$$ and $$\mu_0$$ are the electric permittivity and magnetic permeability of free space respectively. If the corresponding quantities of a medium are $$2 ~\epsilon_0$$ and $$1.5 ~\mu_0$$ respectively, the refractive index of the medium will nearly be :

A horizontal ray of light is incident on the right angled prism with prism angle $$6^{\circ}$$. If the refractive index of the material of the prism is 1.5 , then the angle of emergence will be:

An object is mounted on a wall. Its image of equal size is to be obtained on a parallel wall with the help of a convex lens placed between these walls. The lens is kept at distance x in front of the second wall. The required focal length of the lens will be :