Beams of light are incident through the holes A and B and emerge out of box through the holes C ndas......

Beams of light are incident through the holes A and B and emerge out of box through the holes C – and D respectively, as Box shown in the figure.

Which of the following could be inside the box?

Here, the emergent rays are parallel to the direction of the incident ray. Therefore, a rectangular glass slab could be inside the box as the extent of bending of light ray at the opposite parallel faces AB (air-glass interface) and CD (glass-air interface) of the rectangular glass slab are equal and opposite. This is why the ray emerges parallel to the incident ray.

By: santosh