Where is the largest telescope in India? What is the diameter of the objective in it?

An object is clearly seen through an astronomical telescope of length $50 \ cm$. The focal lengths of its objective and eyepiece,respectively,can be

Magnifying power of an astronomical telescope for normal adjustment is $10$ and the length of the telescope is $110 \ cm$. The magnifying power of the same telescope,when the image is formed at the near point,is:

The focal lengths of the objective and eye lenses of a telescope are respectively $200 \, cm$ and $5 \, cm$. The maximum magnifying power of the telescope will be:

$A$ simple telescope, consisting of an objective of focal length $60\, cm$ and a single eye lens of focal length $5\, cm$, is focused on a distant object in such a way that parallel rays emerge from the eye lens. If the object subtends an angle of $2^o$ at the objective, the angular width of the image is........$^o$.

In a reflecting telescope,a secondary mirror is used to: