Question

If your eye glasses have focal length 60 cm, what is your near point? [2 MARKS]

Answer 1

Problem: 2 Marks

Given:

f = 60cm, also f is positive, it is a case of Hypermetropia.
we need the object to be at near point of distinct vision for a normal eye i.e, at 25cm.
let u = -25cm (near point of normal eye)

according to Lens formula:
$\frac{1}{f}=\frac{1}{v}-\frac{1}{u}$

$\frac{1}{60}=\frac{1}{v}+\frac{1}{25}$

v = -43cm, thus near point is 43 cm.