Define the power of a lens.

Explanation

### Step-by-Step Solution:

1. **Definition of Power of a Lens**: The power of a lens is defined as the degree to which it converges or diverges light rays that pass through it.

2. **Understanding Convergence and Divergence**: When parallel rays of light pass through a converging lens (convex lens), they meet at a point called the focal point. Conversely, a diverging lens (concave lens) causes parallel rays to spread out.

3. **Mathematical Representation**: The power of a lens (P) can be mathematically expressed as the reciprocal of its focal length (f) in meters:
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