Question

A person cannot see the object beyond 200cm. The power of lens used to correct the vision will be :

• A. +0.5 D
• B. +5D
• C. -0.5D
• D. -5D

Answer 1

The correct option is C -0.5D

Here for the lens needed , it should form image of an distant object. at distance of $200cm$

Here, $u=\infty$ and $v=-200cm$

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

$\Rightarrow \frac{1}{f}=-\frac{1}{200}+0$

$\Rightarrow f=-2m$

$\Rightarrow P\left(inD\right)=\frac{1}{f\left(inm\right)}=-0.5D$

Therefore, C is correct option.