The focal lengths of the objective and eyepiece of an astronomical telescope are 50 cm and 5 cn respectively. Find the tube length and the magnification for parallel vision.

The focal length of the objective and eye piece of a telescope are respectively 2m and 5 cm. The maximum magnifying power will be

The focal lengths f_(o) and f_(e) of an astronomical telescope at 30 cm and 6 cm respectively. What is the distance between its objective and eyepiece when set for normal adjustment ?