Question

A plane mirror $M$ is arranged parallel to a wall $W$ at a distance from it. The light produced by a point source $S$ kept on the wall is reflected by the mirror and produces a patch of light on the wall. The mirror moves with velocity v towards the wall.

• A. The patch of light will move with speed v on the wall
• B. The patch of light will not move on the wall
• C. As the mirror comes closer, the patch of light will become larger and shift away from the wall with speed larger than v
• D. The size of the patch of light on the wall remains the same

Answer 1

Answer: (B), (D)

The correct options are
B The patch of light will not move on the wall
D The size of the patch of light on the wall remains the same

From the above ray diagram, it is clear that the option (b) and (d) are correct.