A machinist with normal vision has a near point at 25 cm.This machinist wears +4.25-diopter eyeglasses in order to do very close work.With these eyeglasses,what is the near point of the machinist? Assume that he wears the glasses extremely close to his eyes.
A)12 cm
B)10 cm
C)7 cm
D)15 cm
E)17 cm

Question

Quizplus · Accepted Answer

The near point with eyeglasses can be calculated using the lens formula: 1/f = 1/v - 1/u, where f is the focal length of the lens, v is the image distance (in this case, the new near point), and u is the object distance (the original near point). For a +4.25 diopter lens, f = 1/D = 1/4.25 m = 0.235 m (or 23.5 cm). Since the glasses are worn very close to the eyes, we can assume the image is formed at the near point of the eyes without the glasses, which is 25 cm. Substituting these values into the lens formula gives us the new near point closer than the original 25 cm, specifically at 12 cm.

A Machinist with Normal Vision Has a near Point at 25