What is the principal axis of a spherical mirror ?

Explanation

### Step-by-Step Solution:

1. **Understanding the Structure of a Spherical Mirror:**
- A spherical mirror is a mirror that has the shape of a portion of a sphere. It can be either concave or convex.

2. **Identifying Key Points:**
- In a spherical mirror, there are two important points:
- **Center of Curvature (C):** This is the center of the sphere from which the mirror is a part.
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