For a fixed incident light ray, if the mirror be rotated through and angle `theta` (about an axis which lies in the plane of mirror and perpendicular to the plane of incidence), show that the reflected ray turns through an angle 2`theta` in same sense.

Explanation

To solve the problem, we need to analyze the behavior of light rays when they reflect off a mirror that is rotated. Let's break it down step by step.

### Step-by-Step Solution:

1. **Understand the Setup**:
- We have a mirror and a fixed incident light ray. The incident light ray makes an angle \( \phi \) with the normal to the mirror surface.
- The mirror is rotated through an angle \( \theta \) about an axis that lies in the plane of the mirror and is perpendicular to the plane of incidence.

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