An object is clearly seen through an astronomical telescope of length $50 \mathrm{~cm}$. The focal lengths…
An object is clearly seen through an astronomical telescope of length $50 \mathrm{~cm}$. The focal lengths of its objective and eyepiece respectively, can be
$5 \mathrm{~cm}$ and $45 \mathrm{~cm}$
$45 \mathrm{~cm}$ and $-5 \mathrm{~cm}$
$-45 \mathrm{~cm}$ and $-5 \mathrm{~cm}$
$45 \mathrm{~cm}$ and $5 \mathrm{~cm}$
Solution
$\ell=f_{0}+f_{e} ; \quad f_{0}$ and $f_{0}$ are positive.
Magnifying power $=\frac{f_{0}}{f_{e}}>1$