Question

A parallel narrow-beam of light is falling normally on a glass sphere. It will come to a focus

• A. Inside the sphere (except at its centre)
• B. On the surface of the sphere
• C. Outside the sphere
• D. Exactly at the centre of the sphere

Answer 1

Answer: (C)

Outside the sphere

Answer 2

Consider a parallel beam of light falling normally on a glass sphere.
One of the ray passes undeviated through center $C$ as shown, other ray $A B$ follows the path ABDI and forms image $I$, outside the sphere. $N_{1}$ and $N_{2}$ are normal to the spherical surfaces.