Q. A man can see the objects upto a distance of one metre from his eyes. For correcting his eye sight so that he can see an object at infinity, he requires a lens whose power is Or A man can see upto $100\ cm$ of the distant object. The power of the lens required to see far objects will be
A) +0.5 $D$
B) $+ 1.0\ D$
C) $+ 2.0\ D$
D) $- 1.0\ D$
Explanation
(d) The image of object at infinity should be formed at $100\ cm$ from the eye
$\frac{1}{f} = \frac{1}{\infty} - \frac{1}{100} = - \frac{1}{100}$
So the power $= \frac{- 100}{100} = - 1\ D$
[Distance is given in $cm$ but $P = \frac{1}{f}$ in $metres$]
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.