Question

A eye specialist prescribes a number+4.5D to a person for his glasses . What is the focal length of the lens

Answer 1

Answer:

0.22 m or 22.22cm

Explanation:

As P=1/f

=>f=1/P

=>f=1/4.5

=>10/45

or,2/9

Therefore f = 0.22m or 22.22cm.