Question

Q. 6. What is meant by power of a lens ? Write the SI
unit. A student uses a lens of focal length 40 cm
and another of - 20 cm. Write the nature and power
of each lens.
U [CBSE Delhi/OD, 2018]​

Answer 1

Answer:

the answer is given here

Explanation:

Power of lens is defined as the reciprocal of the focal length of the lens expressed in meter. SI unit of power is Dioptre denoted by D. Since the focal length is positive, so it is a convex lens. Since the focal length is negative, so it is a concave lens.