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)5.6
C)6.9
D)7.5
E)8.1

Question

Quizplus · Accepted Answer

The angular magnification (M) of a magnifier is given by the formula M = 1 + (D/f), where D is the near point of the viewer (in meters) and f is the focal length of the lens (also in meters). Here, D = 25 cm = 0.25 m and f = 40 mm = 0.04 m. Plugging these values into the formula gives M = 1 + (0.25/0.04) = 1 + 6.25 = 7.25. However, since this exact value is not an option and considering the context of the question, it seems there might have been a slight miscalculation in the explanation process. The correct approach to calculate angular magnification for a magnifier when the object is at the focal point is actually M = D/f, not 1 + D/f, because the image is formed at infinity, making the first term (1) irrelevant in this specific context. Therefore, M = 0.25 / 0.04 = 6.25, which rounds or approximates to the closest provided option, 6.3.

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