Question

What is the si unit of magnification produced by a lens?

Answer 1

It has not unit because magnification is itself a ratio and cannot have is own si unit

Answer 2

Magnification is a ratio of two same quantities and it is a consent number.

Dioptre or dioptre is a unit of measurement of optical power of a lens.

Same measurements are also applied for the curved mirror.

This is equal of the reciprocal of focal length measured in metres and the formulation of this measurement is (1 dioptre = 1 m−1.).