Two converging lenses, the first with focal length 10.0 cm and the second with focal length 20.0 cm, are separated by 40.0 cm. An object, 3.00 cm in height, is placed 30.0 cm in front of the first lens. Where is the final image formed?
A) 11.1 cm after the second lens
B) 100 cm after the second lens
C) 45.0 cm after the second lens
D) 5.00 cm after the second lens
E) 5.00 cm before the second lens

Question

Quizplus · Accepted Answer

First, find the image formed by the first lens using the lens formula: 1/f = 1/do + 1/di. For the first lens, f = 10 cm and do = 30 cm, giving di = 15 cm. This image acts as the object for the second lens, located 40 - 15 = 25 cm from it. Using the lens formula again for the second lens with f = 20 cm and do = 25 cm, we find di = 100 cm. Thus, the final image is 100 cm after the second lens.

Two Converging Lenses, the First with Focal Length 10