A farsighted boy has a near point at 2.2 m and requires eyeglasses to correct hi

Question

A farsighted boy has a near point at 2.2 m and requires eyeglasses to correct his vision. Corrective lenses are available in increments in power of 0.25 diopters. The eyeglasses should have lenses of the lowest power for which the near point is no further than 25 cm. The correct choice of lens power for eyeglasses, in diopters, is: A farsighted boy has a near point at 2.2 m and requires eyeglasses to correct his vision. Corrective lenses are available in increments in power of 0.25 diopters. The eyeglasses should have lenses of the lowest power for which the near point is no further than 25 cm. The correct choice of lens power for eyeglasses, in diopters, is:

Explanation / Answer

Apply 1/f = 1/p+ 1/q

We need to take objects at 25 cm and form images at 2.2 m

1/f = 1/25 + 1/-220

f = 28.21

D = 1/f converted to meters

D = 1/.2821

D = 3.55

Since it has to be in .25 increments, D = 3.75

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