Question:
A person cannot see distinctly objects kept beyond 2 m. This defect can be corrected by using a lens of power
(a) +0.5 D
(b) -0.5 D
(c) +0.2 D
(d) -0.2 D
Solution:
(b).
Explanation : Person is suffering from myopia. Focal length of the lens used to correct the defect, f = – d = – 2 m
$\therefore$ Power of lens, $\mathrm{P}=\frac{1}{f}=-\frac{1}{2 m}=-0.5 \mathrm{D}$