Q. Two similar plano-convex lenses are combined together in three different ways as shown in the adjoining figure. The ratio of the focal lengths in three cases will be
A) $2\ :2\ :1$
B) $1\ :1\ :1$
C) $1\ :2\ :2$
D) $2\ :1\ :1$
Explanation
(b) In each case two plane-convex lens are placed close to each other, and $\frac{1}{F} = \frac{1}{f_{1}} + \frac{1}{f_{2}}$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.