Question

A person suffering from myopia (short-sightedness) can see clearly only up to a distance of 2m.What is the power of concave lens required to rectify this defect?

• A. $-0.5D$
• B. $-1.5D$
• C. $-2.0D$
• D. $-2.5D$

Answer 1

Answer: (A)

$-0.5D$

The distance of far point $X=2m$

To view distant object clearly, concave lens of focal length $-2m$ should be used.

i.e. $f=-X=-2m$

Power of lens =$P=\frac{1}{f}=\frac{1}{-2}=-0.5D$