Three converging lenses of focal length 5 cm are arranged with a spacing of 20 cm between them,and are used to image an insect 20 cm away from the first lens.Where is the image with respect to the third lens?
A)-4.3 cm
B)-2.1 cm
C)2.5 cm
D)5.4 cm
E)8.6 cm

Question

Quizplus · Accepted Answer

The image formed by the first lens is at infinity since the object is at its focal point (20 cm away). The second lens, with the object at infinity, forms an image at its focal point, 5 cm away. This image acts as the object for the third lens, which is 20 cm away from the second lens. Using the lens formula for the third lens, the image is formed at 8.6 cm from the third lens.

Three Converging Lenses of Focal Length 5 Cm Are Arranged