A simple magnifier of refractive power 15.0 D is used to observe a beetle on a student's desk.If the image of the beetle is formed at her nearpoint of 25 cm,how far is the beetle from the magnifier?
A) 50 cm
B) 6.3 cm
C) 4.2 cm
D) 17 cm

Question

Quizplus · Accepted Answer

The formula for the focal length (f) is f = 1/D, where D is the refractive power. For 15.0 D, f = 1/15 = 0.0667 m or 6.67 cm. Using the lens formula 1/f = 1/v - 1/u, where v = 25 cm (image distance) and f = 6.67 cm, solving for u (object distance) gives approximately 4.2 cm.

A Simple Magnifier of Refractive Power 15