Question

A person's near point is 50 cm and his far point is 3 m. Power of the lenses he requires for (i) reading and
(ii) for seeing distant stars are

• A. – 2 D and 0.33 D
• B. 2 D and – 0.33 D
• C. – 2 D and 3 D
• D. 2 D and – 3 D

Answer 1

The correct option is B 2 D and – 0.33 D

For correcting the near point, required focal length

$f=\frac{50\times 25}{(50-25)}=50cm$
so power $p=\frac{100}{50}=+2D$

For correcting the far point, required focal length
f = -(far point of defective eye) = -3m

$\therefore P=-\frac{1}{3}D=-0.33D$