Define the following terms in the context of spherical mirrors: Pole

Explanation

### Step-by-Step Text Solution:

1. **Understanding Spherical Mirrors**:
- Spherical mirrors are mirrors that have the shape of a section of a sphere. They can be either concave (curved inward) or convex (curved outward).

2. **Defining the Principal Axis**:
- The principal axis is an imaginary line that passes through the center of the spherical mirror and is perpendicular to the surface of the mirror.

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