Draw a labelled ray diagram of a refracting telescope when it forms image of a distant object at infinity. Derive the expression for its magnifying power.
Show Hint
For a refracting telescope in normal adjustment:
\[
L=f_o+f_e
\]
and
\[
M=-\frac{f_o}{f_e}
\]
A large focal length objective and a small focal length eyepiece give a high magnifying power.