Define power of lens and give its relation with focal length.

Explanation

### Step-by-Step Solution

1. **Definition of Power of a Lens**:
The power of a lens is defined as its ability to converge (bring together) or diverge (spread apart) light rays that pass through it.

2. **Mathematical Relation**:
The power (P) of a lens is mathematically defined as the reciprocal of its focal length (f) measured in meters. This can be expressed as:
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