A lens of focal length 40 mm is used as a magnifier. The object being viewed is 5.3 mm long, and is positioned at the focal point of the lens. The user of the magnifier has a near point at 25 cm. What
Is the angular magnification of the magnifier?
A) 6.3
B) 8.1
C) 6.9
D) 7.5
E) 5.6

Question

Quizplus · Accepted Answer

When an object is placed at the focal point of a lens, the angular magnification (M) is given by M = 1 + (D/f), where D is the near point distance (25 cm) and f is the focal length (4 cm). Substituting the values, M = 1 + (25/4) = 7.25, which is closest to 6.3.

A Lens of Focal Length 40 Mm Is Used as a Magnifier