A certain converging lens has a focal length of 25 cm. To obtain a combination of power of 3.0 diopters, the lens should be combined with a second
A) diverging lens of focal length 5.0 cm.
B) diverging lens of focal length 8.0 cm.
C) diverging lens of focal length 100 cm.
D) converging lens of focal length 100 cm.
E) converging lens of focal length 8.0 cm.

Question

Quizplus · Accepted Answer

The power of a lens is given by the formula P = 1/f (in meters). The power of the converging lens is 1/0.25 = 4 diopters. To achieve a total power of 3 diopters, the second lens must have a power of 3 - 4 = -1 diopter. A diverging lens with a focal length of 100 cm (1 meter) has a power of -1 diopter.

A Certain Converging Lens Has a Focal Length of 25