An individual is nearsighted; his near point is 18.0 cm and his far point is 40.0 cm.
(a) what lens power is needed to correct his nearsightedness?
-2.5diopters
(b) when the lenses are in use, what is this person's near

Answer

given,

near point = 18 cm

far point = 40 cm

a) The lens should form an upright, virtual image at far point from the distant object.

therefore, f = q  = -40 cm = -0.4 m

where f is the focal length.

the required power

       P = -2.5 D

b) If the lens is used the Person's near point

The lens should form an upright, virtual image at near point from the distant object should be q = - 18 cm = -0.18 m

     p = 32.72 cm

The person's near point is 32.72 cm

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