a farsighted boy has a near point at 2.0m and requires eyeglasses to correct his

Question

a farsighted boy has a near point at 2.0m and requires eyeglasses to correct his vision. corrective lenses are available in increments in power of .25 diopters. the eyeglasses should have lenses of the lowest power for which the near point is no further than 25 cm. the boy borrows eyeglasses that have a power or +2.75 diopters (power of a lens is reciprocal of the focal length and it has unit of diopters). with these eyeglasses, the near of the boy, in cm is closest too:

A.40 B.33 C.37 D.28 E.31

Explanation / Answer

here by using the formula

f = 1 / P

then

1 / v + 1 / u = 1 / f = P

v = 1 / ( 2.75+1/2)

v = 0.31

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