Problem 25.20: Contact lenses Contact lenses are placed right on the eyeball, so

Question

Problem 25.20: Contact lenses Contact lenses are placed right on the eyeball, so the distance from the eye to an object (or image) is the same as the distance from the lens to that object (or image). A certain person can see distant objects well, but his near point is 50.0cm from his eyes instead of the usual 25.0cm . Part A Is this person nearsighted or farsighted? Part B What type of lens (converging or diverging) is needed to correct his vision? Part C If the correcting lenses will be contact lenses, what focal length lens is needed? Part D What is the power corresponding to the focal length found in part (C) in diopters?

Explanation / Answer

A) THis person is farsighted

B) A coverging lense is needed to correct his vision

C)
U = infinite (object distnace)

V = 50 cm

now Apply,

1/f = 1/u + 1/v

1/f = 1/infinite + 1/50

f = 50 cm

d) power = 1/f

= 1/0.5

= 2 diaptors

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