Question

A person with myopic vision see objects only up to a distance of 0.25 m. To be able to read a book placed at the distance of 0.50 m from the eyes, the spectacles needed by this person have power of

• A. -1.0D
• B. -1.5D
• C. -2.0D
• D. +2.0D

Answer 1

The correct option is C -2.0D

$\begin{array}{c}\Rightarrow v=0.25\\ \Rightarrow u=0.5\\ \Rightarrow \frac{1}{v}-\frac{1}{u}=\frac{1}{f}\\ \Rightarrow \frac{-100}{25}+\frac{10}{5}=\frac{-100+50}{25}=\frac{-50}{25}\\ \Rightarrow \frac{1}{f}=-2\\ \Rightarrow f=-o.5m\\ \Rightarrow power=\frac{1}{f_{cm}}\times 100\\ Hence,\\ P=-2D\end{array}$

$\therefore$ option $C$ is correct answer.