Question

We combined a convex lens of focal length $f_{1}$ and concave lens of focal length $f_{2}$ and their combined focal length was $F$. The combination of these lenses will be have like a concave lens, if:

• A. $f_{1}\le f_{2}$
• B. $f_{1}=f_{2}$
• C. $f_{1}< f_{2}$
• D. $f_{1} > f_{2}$

Answer 1

Answer: (D)

If one of the lens is convex and the other is concave, then it behaves like concave lens, if $f_{1} >f_{2}$ and it behaves like a convex lens if $f_{1}< f_{2}$. And it behave like a plane mirror if $f_{1}=f_{2}$.