# A RAY OF LIGHT STRIKES A PLANE MIRROR AT AN ANGLE OF INCIDENCE OF 35°. IF THE MIRROR IS ROTATED THROUGH 10°, THROUGH WHAT ANGLE IS THE REFLECTED RAY ROTATED

- A. 70°
- B. 45°
- C. 25°
**D. 20° ✓**

The answer to the question is: **D. 20°**

When a ray of light strikes a plane mirror, the angle of incidence is equal to the angle of reflection. According to the law of reflection, the angle of incidence is the angle between the incident ray and the normal to the surface at the point of incidence, and the angle of reflection is the angle between the reflected ray and the normal to the surface at the point of reflection. Therefore, if a mirror is rotated through an angle, the reflected ray will also be rotated through twice that angle.

In this case, when a ray of light strikes a plane mirror at an angle of incidence of 35° and the mirror is rotated through 10°, the reflected ray will be rotated through twice that angle. Therefore, the angle through which the reflected ray is rotated can be calculated as follows:

**Angle of rotation of reflected ray = 2 * Angle of rotation of mirror = 2 * **

**10° = 20°**

Therefore, when the mirror is rotated through 10°, the reflected ray will be rotated through an angle of 20°.