An object is placed 40 cm in front of a lens of focal length 40 cm. A second lens is placed 17 cm beyond the first. An image forms 48 cm past the second lens. The lateral magnification of this system is
A)-2.8.
B)-1.2.
C)1.2.
D)2.8.
E)impossible to determine with the information given.

Question

Quizplus · Accepted Answer

The first lens forms an image at infinity since the object is at the focal point (40 cm). The second lens then forms an image 48 cm past it, with an object distance of 17 cm. The magnification of the second lens is -48/17 = -2.8. The total magnification is the product of the magnifications of the two lenses, which is 1 * -2.8 = -2.8. However, the question asks for lateral magnification, which is the absolute value, so the answer is 1.2.

An Object Is Placed 40 Cm in Front of a Lens