Question

A person needs a lens of power -4.5 D for correction of her vision. What is the focal length of the corrective lens?

• A. $f=-0.25m$
• B. $f=+0.22m$
• C. $f=1.22m$
• D. $f=-0.22m$

Answer 1

The correct option is D $f=-0.22m$

$f=\frac{1}{P}=\frac{1}{-4.5}=-0.22m$