Question

The near point of a long-sighted person is 50 cm from the eye.
(a) Can she see clearly an object at:
(i) a distance of 20 cm?
(ii) at infinity?
(b) To read a book held at a distance of 25 cm, will she need converging or diverging spectacle lenses?

Answer 1

(a) (i) A long-sighted person who has a near point of 50 cm from the eye cannot clearly see an object kept at a distance of 20 cm. She can see an object only if it is kept at her near point of 50 cm in front of the eye.
(ii) As the person is long-sighted, she cannot see nearby objects, but can see distant objects, clearly. Therefore, she can clearly see the object kept at infinity.
(b) To read a book held at a distance of 25 cm, the person, who is long-sighted, will need converging lenses.