Question

Determine the power of lens of a converging lens of focal length 20cm.

Answer 1

Explanation:

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.

d=1/20

=0.05

Answer 2

Given ,

Focal length of converging lens (f) = 20 cm

We know that , the reciprocal of focal length is called power of lens

$\boxed{ \tt{Power \: of \: lens (P) = \frac{1}{f \: \: (in \: m)} }}$

Thus ,

P = 1/0.2

P = 5 D

Therefore , the power of lens is 5 D