Define one dioptre of power of a lens.

Explanation

**Step-by-Step Solution:**

1. **Understanding Power of a Lens**: The power of a lens is defined as the ability of the lens to converge or diverge light rays. It is mathematically expressed as the reciprocal of the focal length of the lens in meters.

2. **Formula for Power**: The formula for calculating the power (P) of a lens is given by:
\[ P = \frac{1}{f} \]
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