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
For correcting the near point, required focal length
f=50×25(50−25)=50 cm
so power p=10050=+2D
For correcting the far point, required focal length
f = -(far point of defective eye) = -3m
∴P=−13D=−0.33 D