Question

An individual is nearsighted; his near point is 13.0 cm and his far point is 50.4 cm. what lens power is needed to correct his nearsightedness?

Answer 1

Answer:

= -1.984 Diopters

Explanation:

The lens should form an upright, virtual image at the far point.

Therefore;

The image distance, V will be -50.4 cm, since the image is virtual.

For objects at very far distant the object distance,u, will be ∞ ; This means that focal length, f, will be equivalent to image distance, v, that is -50.4 cm

Therefore; f = -50.4/100 = -0.504 m

But, since Power of a lens, P, is given by the reciprocal of focal length in meters, (1/f)

Then, power will be given by;

Power = 1/f

           = 1/-0.504 m

           =- 1.984

Power is measured in Diopters

Hence          = -1.984 Diopters