### NEET Solved Paper 2017 Question 26

##### Question: 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 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

#### Options:

A) $ \frac{x}{y} $

B) $ \frac{y}{2x} $

C) $ \frac{y}{x} $

D) $ \frac{x}{2y} $

## Show Answer

#### Answer:

Correct Answer: B

#### Solution:

When mirror is rotated by $ \theta $ angle reflected ray will be rotated by $ 2\theta . $ $ \frac{y}{x}=2\theta $ $ \theta =\frac{y}{2x} $