A converging lens of focal length `5.0cm` is placed in contact
with a diverging lens of focal length `10.0cm.` Find the combined focal length of
the system.

Answer

A, C

Explanation

Here, `f_1=+5.0cm and f_2=-10.0cm`
Therefore, the combined focal length F is given by
`1/F=1/(f_1)+1/(f_2)=1/5.0-1/10.0=+1/10.0`
`:. F=+10.0 cm`
i.e. the combination behaves as a converging lens of focal length `10.0cm`