A beam of light from a source L is incident normally in a plane mirror 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 mirror 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-

Question

( A ) $\frac{x}{y}$
( B ) $\frac{y}{2x}$
( C ) $\frac{x}{2y}$
( D ) $\frac{y}{x}$