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

Explanation

Tele means away and scope means to see. Hence telescope name is given for purpose to see the things which are away.
The optical instrument used to observe the objects which are far away is called telescope.
Types of telescope :
1) Astronomical telescope : The objects which are far away like Sun, Stars, Planets, etc. can be observed by this telescope. The final image obtained in this is inverted and diminished but as the objects are spherical, there is no effect on image.
2) Terrestrial telescope : There is an additional pair of inverting lens in this telescope which will make the final image erect. Galileo used convex and concave lens in this telescope.
3) Refracting telescope : Concave mirror is used in this telescope in place of objective. E.g. : Cassegrain telescope.