A light ray is incident normally on a plane mirror.
What is its angle of incidence?

Explanation

To solve the question, "A light ray is incident normally on a plane mirror. What is its angle of incidence?", we can follow these steps:

### Step-by-Step Solution:

1. **Understanding the Terms**:
- The angle of incidence is defined as the angle between the incident ray and the normal (a line perpendicular to the surface of the mirror at the point of incidence).

2. **Identifying the Situation**:
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