7. A beam of 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 1. When the mirror is rotated through a small angle θ, the spot of the light is found to move through a distance y on the scale. The angle θ is given by ?

7. A beam of 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 1. When the mirror is rotated through a small angle θ, the spot of the light is found to move through a distance y on the scale. The angle θ is given by ?

(a) \( \frac{y}{x} \)

(b) \( \frac{x}{2y} \)

(c) \( \frac{x}{y} \)

(d) \( \frac{y}{2x} \)

Answer :  (d) \( \frac{y}{2x} \)

\( \tan(2\theta) = \frac{y}{x} \)

\( 2\theta = \frac{y}{x} \)

\( \theta = \frac{y}{2x} \)