Question

b) Find the power of a convex lens of focal length 20 cm
an​

Answer 1

A diopter is the unit of measure for the power of a refractive index of a lens.

It is usually the reciprocal of the focal length of a lens.

It is denoted by D.

Formulae :

D = 1/f where F is the focal length and D is the power of the lens in Diopter.

From the question above given the focal length is 20cm we can get the power of the lens using this formula.

We first convert the cm to meters :

20/100= 0.2m

D=1/0.2

=5 Diopters

Answer 2

Answer:

Given: Focal length, f= 20 cm =0.2m

Explanation:

Power= 1/ focal length in m= 1/0.2 = 5D