Eye piece of an astronomical telescope has focal length of 5 cm. If angular magnification in normal adjustment is 10, then dustance between eye piece and objective should be

15 cm 35 cm 55 cm 75 cm

55 cm

In normal adjustment, $L = f_0 + f_e$ and $M=\frac{f_0}{f_e}$ or $10=\frac{f_0}{5}⇒f_0=50cm$ ∴ L = 5 cm + 50 cm = 55 cm.