Draw a labelled ray diagram to show the image formation in a refracting type astronomical telescope in the normal adjustment position. Write two drawbacks of refracting type telescopes. OR (a)Define resolving power of a telescope. Write the factors on which it depends. (b) A telescope resolves whereas a microscope magnifies. Justify the statement.

Question

Philoid · Accepted Answer

Ray diagram of the image formation in a refracting type astronomical telescope in the normal adjustment position,

The two main drawbacks with an astronomical telescope are: -

1. Refracting telescopes of practical applications are made of very large and thick lenses, such big lenses are very heavy and therefore, difficult to make and support by their edges.

1. Manufacturing such large sized lenses is difficult and expensive which form images that are free from any kind of chromatic aberration and distortions.

OR

a) Resolving power of a telescope is defined as the ability of a telescope to distinguish two close images as being separate. An example of resolving power is how well a telescope can show two stars as being separate stars.

It depends upon the area of the objective and on the diameter of the objective.

b) A microscope produces magnified images of very small near objects. On the other hand, a telescope produces image of far objects nearer to our eye. Objects which are not resolved at far distance, can be resolved by telescope.