An astronomical refracting telescope has an objective of focal length $20 \, m$ and an eyepiece of focal length $2 \, cm$. Then:

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

In a simple telescope,the focal length of the objective lens is $f_o = 60 \ cm$ and the focal length of the eyepiece is $f_e = 5 \ cm$. If the rays coming from the object make an angle of $2^\circ$ at the objective,then the angular magnification (angular size of the image) is ........... $^\circ$.

An observer looks at a tree of height $15 \ m$ with a telescope of magnifying power $10$. To him,the tree appears

$A$ 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........$^o$.

$A$ telescope has an objective lens of focal length $144\, cm$ and an eyepiece of focal length $6\, cm$. Find the magnifying power of the telescope for normal adjustment.