A magnifying glass has a converging lens of focal length of 18.6 cm. At what distance from a nickel should you hold this lens to get an image with a magnification of +1.67?

Answer 1

f/d = 1.67; f = 1.67d.

1/18.6 = 1/d + 1/f; 1/18.6 = 1/d + 1/(1.67d); 1/18.6 = 2.67/(1.67d); d = 18.6·2.67/1.67 = 29.74 cm