Eyes: A machinist with normal vision has a near point at 25 cm. The machinist wears eyeglasses in order to do close work. The power of the lenses is + 1.75 diopters. With these eyeglasses, what is the near point of the machinist?

Question

Quizplus · Accepted Answer

The power of the lens (P) is given by P = 1/f, where f is the focal length in meters. For a lens power of +1.75 diopters, f = 1/1.75 = 0.571 meters or 57.1 cm. The new near point is calculated using the lens formula: 1/f = 1/v - 1/u, where v is the image distance (near point with glasses) and u is the object distance (original near point). Solving for v with u = -25 cm gives v ≈ 17 cm.

Eyes: a Machinist with Normal Vision Has a near Point