What is meant by a power of a lens? Define its SI unit.
The power of a lens is defined as the reciprocal of its focal length. It is represented by the letter P. The power P of a lens of focal length f is given as
P = 1/f
The SI unit of power is dioptre (D).
Power of lens: Power of lens is defined as its ability to converge or diverge the rays of light falling on it. SI unit of power is Dioptre.