A beam of light from a source `L` is incident normally on a plane mirrorr fixed at a certain distance `x` from the source. The beam is reflected back as a spot on a scale placed just above the source `L`. When the mirrorr is rotated through a small angle `theta`, the spot of the light is found to move through a distance `y` on the scale. The angle `theta` is given by `:`

Options

A. `(y)/(2x)`
B. `(y)/(x)`
C. `(x)/(2y)`
D. `(x)/(y)`

Answer

A

Explanation

On rotating the mirror by an angle `theta` the reflected ray will be rotated by `2theta`.
In the figure given below, O represents the point on the mirror at which the ray of light is incident and A and B are the positions of the spot of light.

From the figure :
`(y)/(x)=2theta`
`rArr" "theta=(y)/(2x)`