Question

A person needs a lens of power +2.5D for correction of his vision.
(a) What kind of defect in vision is he suffering from ?
(b) What is the focal length of the corrective lens?
(c) What is the nature of the corrective lens?

Answer 1

Given,

$P=+2.5D$

(a) Hypermetropia

(b) focal length, $f=\frac{1}{P}$

$f=\frac{100}{2.5}=+40cm$

(c) convex lens