Question

The near point of the hypermetropic eye is 60cm. what is the nature and power of lens required to enable him to read a book placed at 25 cm from the eye?

Answer 1

convex lens of power 0.028 D

Answer 2

Lens formula is given by 1/f = 1/u + 1/v

Here, f is the focal length

u is the distance at which object is placed from lens.

v is the distance of image from lens.

Given details:

v  = -60

u = 25

1/f = 1/25 + 1/(-60)

1/f = 0.04 - 0.0167

1/f = 0.023 / cm

1/f = 2.3 / m

Power of lens is P = 1/f = 2.3 D

Since the power of lens is positive, nature of lens is convex.