Where is the largest reflecting telescope in the world located? Mention the diameter of its reflector.

What is a telescope? Discuss the types of telescopes that are used in general.

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

$(a)$ $A$ giant refracting telescope at an observatory has an objective lens of focal length $15 \; m$. If an eyepiece of focal length $1.0 \; cm$ is used,what is the angular magnification of the telescope?
$(b)$ If this telescope is used to view the moon,what is the diameter of the image of the moon formed by the objective lens? The diameter of the moon is $3.48 \times 10^{6} \; m$,and the radius of the lunar orbit is $3.8 \times 10^{8} \; m$.

The length of a telescope is $36 \ cm$. The focal lengths of its lenses can be

The magnifying power of a telescope is $9.$ When it is adjusted for parallel rays,the distance between the objective and eyepiece is $20\; cm.$ The focal lengths of the lenses are: