Draw a neat labelled diagram of image formed in a refracting telescope. Give the expression for magnification of an object, for an image formed at infinity.

Explanation

Here, `L=f_(0)+f_(e)`.
`tan alpha= -(h)/(f_(0))=alpha` for small angles.
`tan beta= (h)/(f_(e))= beta` for small angles.
and `m= (beta)/(alpha) = - (f_(0))/(f_(e))`. The -ve sign indicates that the final image is inverted.
Note : The largest lens objective in use has a diameter of 40 inches, which is at the Yerkes observatory in Wisconsin, USA.