Define the following terms in the context of spherical mirrors: Principal axis

Explanation

### Step-by-Step Solution:

1. **Understanding Spherical Mirrors**:
- Spherical mirrors are mirrors that have the shape of a portion of a sphere. They can be either concave or convex.

2. **Identifying Key Components**:
- In the context of spherical mirrors, there are several important points:
- **Pole (P)**: The central point of the mirror's surface.
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