Q. We combined a convex lens of focal length $f_{1}$ and concave lens of focal lengths $f_{2}$ and their combined focal length was $F$. The combination of these lenses will behave like a concave lens, if
A) $f_{1} > f_{2}$
B) $f_{1} < f_{2}$
C) $f_{1} = f_{2}$
D) $f_{1} \leq f_{2}$
Explanation
(a) $F = \frac{f_{1}f_{2}}{f_{2} - f_{1}},\ F$ will be negative if $f_{1} > f_{2}$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.