A farsighted boy has a near point at 2.3 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)+ 3.75
B)+ 3.50
C)+ 3.25
D)+ 4.00
E)+ 4.25

Question

Quizplus · Accepted Answer

To correct the near point to 25 cm, we use the lens formula: 1/f = 1/v - 1/u. Here, v = 25 cm = 0.25 m, and u = -2.3 m (since the object is virtual). Solving gives f ≈ 0.267 m, so power P = 1/f ≈ 3.75 diopters.

A Farsighted Boy Has a near Point at 2