The magnifying power of a telescope is high if its objective and eyepiece have respectively

The focal length of an objective of a telescope is $3 \ m$ and its diameter is $15 \ cm$. Assuming that for a normal eye,the diameter of the pupil is $3 \ mm$ for its complete use,the focal length of the eyepiece must be: (in $cm$)

To increase the magnifying power of a telescope ($f_o$ = focal length of the objective and $f_e$ = focal length of the eye lens):

In which type of telescope,an extra pair of inverting lens is available?

The focal length of the objective of an astronomical telescope is $1.5 \ m$. Under normal adjustment,the length of the telescope is $1.56 \ m$. The focal length of the eyepiece is: (in $m$)

What are reflecting type of telescopes? Explain the advantages and disadvantages of reflecting telescopes as compared to refracting telescopes.