Question

The power of lens, a short sighted person uses is $-2D$. The maximum distance of an object which he can see without spectacles is

• A. $25cm$
• B. $50cm$
• C. $100cm$
• D. $10cm$

Answer 1

The correct option is B $50cm$

The maximum distance of an object, which a person can see without spectacles is equal to the focal length of the lens.

Hence, let $focallength=f$

$Power=P=-2D$

$f=\frac{100}{P}$,
$=\frac{100}{-2}cm$
$=-50cm$
So he can see upto a distance of $50cm$, without spectacles.