Question

A person suffering from myopia cannot see beyond 1 m. What should be the focal length of the concave lens that will correct his vision?

Answer 1

So when the object is placed at infinity a image should be formed at 1 m away from eyes.

So , $u=\infty$

$v=-1m=-100cm$

we know that $\frac{1}{f}=\frac{1}{v}-\frac{1}{u}$

$\frac{1}{f}=\frac{1}{-100}-\frac{1}{\infty }$

so $f=-100cm=-1m$

He should use a concave lens with focal length 1m