Question

Question 18 (b)
A person needs a lens of power –4.5 D for correction of her vision.
What is the focal length of the corrective lens?

Answer 1

Given: P = -4.5 D
$f=\frac{1}{p}$
$f=\frac{1}{-4.5}$
$f$ = -0.22 m or -22 cm