question_answer 37)

  Beams of light are incident through the holes A and B and emerge out of box through the holes C and D respectively as shown in the figure. Which of the following could be inside the box? (a) A rectangular glass slab                                           (b) A convex lens (c) A concave lens                                                            (d) A prism

Answer:

                  (A) 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.