Answer:
a
Step-by-step explanation:
The correct answer is a) equal to the angle of rotation.
When a mirror is rotated through a certain angle, the reflected beam also rotates through the same angle. This is because the angle of incidence (the angle between the incident beam and the normal to the mirror) is equal to the angle of reflection (the angle between the reflected beam and the normal to the mirror), and both of these angles are measured with respect to the same plane.
Therefore, if the mirror is rotated through an angle of θ, the incident beam will also rotate through θ to maintain the same angle of incidence, and the reflected beam will rotate through θ to maintain the same angle of reflection. The result is that the reflected beam is rotated through an angle that is equal to the angle of rotation of the mirror.