$A$ reflecting telescope utilizes

What is the tube length of a telescope?

To produce a magnified erect image of a far object,along with a convex lens,we will require:

If the length of the tube of an astronomical telescope is $105 \, cm$ and its magnification power for normal adjustment is $20$,then the focal length of its objective lens will be ....... $cm$.

The magnification power of a telescope is $9$ and the distance between the two lenses is $20 \, cm$. What are the focal lengths of the component lenses?

$A$ telescope has an objective of focal length $50 \text{ cm}$ and an eyepiece of focal length $5 \text{ cm}$. The least distance of distinct vision is $25 \text{ cm}$. The telescope is focused for distinct vision on a scale $200 \text{ cm}$ away. The separation between the objective and the eyepiece is.......$\text{cm}$.