Question

a) State two main considerations taken into account while choosing the objective of
astronomical telescopes ​

Answer 1

Answer:

(a) choice of objective

(b) Ray diagram of reflecting type telescope.

formula of magnifying power

(c) state two advantage

Explanation:

(a) Two main considerations are:

1) The diameter of the objective on which the brightness of the object , resolving power depend.

2) The focal length of the objective on which the magnification (M = fo/fe) depends.

(b) diagram given above

(c)advantages of reflecting type telescope over refracting type telescope :

1) Mirrors do not cause chromatic aberration.

2) Mirrors are easier and cheaper to build.

3) Mirrors are easier to mount because the back of the

mirrors can be used to attach the mount.

4) Image is brighter compared to the image formed in refracting type telescope.

Answer 2

Answer:

1. larger focal length

2.larger aperture

Explanation:

The astronomical telescope make use of two positive lenses

First is objective , which forms the image of a distance object at its focal length and second is eyepiece , which acts as a simple magnifier with

which to view the image formed by the object .

So , the two main considerations taken into account while choosing the objective of astronomical telescopes are :

1. objective  lenses  should have larger focal length because larger focal length enhances the magnifying power of the telescope .
2. and larger aperture surface area to collect more light .

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