If the tube length of astronomical telescope is 105 cm and magnifying power is 20 for normal setting, calculate the focal length of the objective
Answer & explanation
Correct answer: option 1
$L=f_0+f_e$ = 105 cm and M = $\frac{f_0}{f_e}$ = 20
$\Rightarrow f_0$ = 100 cm and $f_e$ = 5 cm