A stamp collector with a normal near point (25 cm)needs a magnifying power of 10 to examine her stamps.What power of magnifying glass should she buy?
A)0.40 diopters
B)2.5 diopters
C)10 diopters
D)40 diopters
E)25 diopters

Question

Quizplus · Accepted Answer

The magnifying power (M) needed is 10, and the near point distance (D) is 25 cm or 0.25 m. The formula for magnifying power when using a magnifying glass is M = 1 + (D/f), where f is the focal length of the lens. Rearranging for f gives f = D/(M-1). Substituting the given values, f = 0.25/(10-1) = 0.25/9 meters = 0.0278 meters. The power (P) of a lens in diopters is given by P = 1/f (in meters), so P = 1/0.0278 = 36 diopters, which is approximately 40 diopters, considering the options provided.

A Stamp Collector with a Normal near Point (25 Cm)needs