A light ray falls normally on a plane mirror. What happens after reflection? 
AIt reflects at $90^\circ$ to the normal.
BIt retraces its path.
CIt travels along the mirror surface.
DIt gets refracted into the mirror.
Answer & Solution
Correct answer: B. It retraces its path.
If a ray falls normally on the mirror, the angle of incidence is $0^\circ$. By the law of reflection, the angle of reflection is also $0^\circ$, so the reflected ray goes back along the same path.
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