Question

A person is able to see objects clearly only when these are lying at distances between 50 cm and 300 cm from his eye.
(a) What kind of defects of vision is he suffering from?
(b) What kind of lenses will be required to increase his range of vision from 25 cm to infinity? Explain briefly.

Answer 1

(a) The person is suffering from both Myopia and Hypermetropia. It is because the range of a normal eye vision is from 25 cm to infinity, where 25 cm is the shortest distance for the distinct vision and infinity is the longest distance for the vision of a normal healthy eye. Since the person can only see the objects lying in between 50 cm to 300 cm, therefore he is suffering from both the defects.

(b) The lense required to increase his range of vision from 25 cm to infinity should be a bifocal lens consists of a concave lens for distant vision and convex lens for near vision.