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

15 cm          35 cm 55 cm    75 cm

55 cm

$\text{In normal adjustments } L = f_0 + f_e $ $ M = \frac{f_0}{f_e} = 10$ $ 10 = \frac{f_0}{5} \Rightarrow f_0 = 50cm$ $ L = f_0 + f_e = 50cm + 5 cm = 55cm$