A narrow beam of light falls on a small plane mirror that can be rotated about a…
PHYSICS · Multi-part · CBSE · Physics · Light — Reflection and Refraction · Light — Reflection and Refraction
Problem
A narrow beam of light falls on a small plane mirror that can be rotated about a vertical axis passing through its centre.
(a) Derive an expression for the angular displacement of the reflected beam when the mirror is rotated through a small angle θ while the incident beam remains fixed.
(b) Using the expression obtained in part (a), determine through what angle the mirror must be rotated so that the reflected beam sweeps through an angle of 90∘.
(c) A student stands 0.50m in front of the mirror, and a wall is located 2.0m behind the student. While the mirror rotates through the angle calculated in part (b), calculate the linear distance traced by the spot of light on the wall.