Question

Define one dioptre. Name the instrument used for measuring the power of a lens.

Answer 1

1. Dioptre is the unit of power.
2. The formula for power$\left(P\right)$is $P=\frac{1}{f}$, where $f$is the focal length of the lens in metre.
3. One dioptre - One dioptre is the power of a lens whose focal length is one metre.
4. The power of a lens is measured by an instrument known as a dioptremeter.