Q 12-09-103JEE MainJEE Main 2023 (30 Jan, Shift 1)Medium
A person has been using spectacles of power $-1.0$ diopter for distant vision and a separate reading glass of power $2.0$ diopters. What is the least distance of distinct vision for this person?
Answer: (D) $50\ \text{cm}$
The reading glass ($f=50\ \text{cm}$) must form a virtual image at the person's near point $d$ of an object held at $25\ \text{cm}$:
$$\frac1v-\frac1u=\frac1f\ \Rightarrow\ \frac1{-d}+\frac1{25}=\frac1{50}\ \Rightarrow\ \frac1d=\frac1{50}\ \Rightarrow\ d=50\ \text{cm}$$
Solution by Sreeraj P, M.Sc Physics