A beam cf light from a source L is incident normally on 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

$\begin{array}{1 1} (1) \frac{y}{2x} \\ (2) \frac{y}{x} \\ (3) \frac{x}{2y} \\ (4) \frac{x}{y} \end{array}$