A small mirror of mass m is suspended by a massless thread of length . Then the small angle through which the thread will be deflected when a short pulse of laser of energy E falls normal on the mirror
( speed of light in vacuum and acceleration due to gravity)
( speed of light in vacuum and acceleration due to gravity)
- (A)
- (B)
- (C)
- (D)✓ Correct
Answer: (D)
Solution
The laser pulse of energy reflecting normally from the mirror delivers a momentum , giving the mirror an initial speed . As it swings up through a small angle , energy conservation gives Hence , and The thread is deflected through .
JEE Main · 2025 · 04 Apr 2025 · Shift 1 · Single correct option