Question

If the distance of the far point, for a myopic person, is doubled, the focal length of the lens required to correct his/her vision should be -

• A. halved.
• B. kept the same.
• C. doubled.
• D. quadrupled.

Answer 1

The correct option is C doubled.

For a myopic person,

$u=-\infty ,v=\text{far point of the myopic person}$

Now, using,

$\frac{1}{f}=\frac{1}{v}-\frac{1}{u}$

$\Rightarrow \frac{1}{f}=\frac{1}{v}-\frac{1}{(-\infty )}$

$\therefore f=v$

So, if the distance of the far point is doubled, the focal length of the lens should also be doubled.

Hence, option $\left(C\right)$ is the correct answer.