A person cannot see the objects distinctly, when placed at a distance less than `100 cm`. What is the power of the spectacles that he should use to see clearly the objects placed at `25 cm` ?

Explanation

Here, distance of near point, `x' = 100 cm`, distance of object, `d = 25 cm, f = ?, P = ?`
From, `f = (x'd)/(x' - d), = (100 xx 25)/(100 - 25) = (100)/(3) cm`
Thus, `P = (100)/(f) = (100)/(100//3) = 3 D`.
The corrective lens is convex.