Question

The near point of a farsighted person's uncorrected eyes is 80 cm. what power contact lens should be used to move the near point to 25 cm from this person's eyes?

Answer 1

To solve this problem, we will get f and then we will use it to calculate the power.

So, for this farsighted person,
do = 25 cm and di = -80
Therefore:
1/f = (1/25) + (1/-80) = 0.00275 = 0.275 m

Power = 1/f = 1/0.275 = +3.6363 Diopeters.
This means that the lens is converging.