A thin lens of focal length 20 cm is placed in contact with a 20-diopter thin lens.What is the power of the combined lenses?
A)1/2 diopter
B)15 diopters
C)25 diopters
D)40 diopters

Question

Quizplus · Accepted Answer

The power of a lens in diopters is given by the inverse of its focal length in meters. A 20 cm focal length lens has a power of 5 diopters (1/0.2 m). The combined power of two lenses in contact is the sum of their powers: 5 diopters + 20 diopters = 25 diopters.

A Thin Lens of Focal Length 20 Cm Is Placed