The focal length of objective of an astronomical telescope is 1 m. If the magnifying power of telescope is 20, then what is length of telescope for relaxed eye?
Answer & explanation
Correct answer: option 3
Magnification of astronomical telescope for relaxed eye is m = $\frac{f_0}{f_e}$
$f_0= 100cm$
m = 20
$\Rightarrow f_e = 5 cm$
Length of the telescope L = $f_0+f_e$= 105cm