The correct option is Dioptre.
Explanation
The power of a lens is a measure of its ability to converge or diverge light rays falling on it. It is mathematically defined as the reciprocal of the focal length ($f$) of the lens, measured in meters. The formula is given by $P = \frac{1}{f}$.
Analysis of Options
- Dioptre Dioptre: Correct. The SI unit of the power of a lens is the Dioptre (symbol: D). One Dioptre is equivalent to the power of a lens whose focal length is one meter ($1 \text{ D} = 1 \text{ m}^{-1}$).
- Tesla Tesla: Incorrect. Tesla (T) is the SI unit of magnetic flux density or magnetic field induction.
- Weber Weber: Incorrect. Weber (Wb) is the SI unit of magnetic flux.
- Lux Lux: Incorrect. Lux (lx) is the SI unit of illuminance, measuring luminous flux per unit area.
Key Takeaway
The power of a lens is the reciprocal of its focal length in meters, and its SI unit is the Dioptre (D).