$A$ reflecting telescope has a large mirror as its objective with a radius of curvature equal to $80 \, cm$. What is the magnifying power of this telescope if the eyepiece used has a focal length of $1.6 \, cm$?

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

The focal length of the objective and the eyepiece of a telescope are $50\,cm$ and $5\,cm$ respectively. If the telescope is focused for distinct vision on a scale distant $2\,m$ from its objective,then its magnifying power will be

An astronomical refracting telescope is being used by an observer to observe planets in normal adjustment. The focal lengths of the objective and eyepiece used in the construction of the telescope are $20\,m$ and $2\,cm$ respectively. Consider the following statements about the telescope:
$(a)$ The distance between the objective and eyepiece is $20.02\,m$.
$(b)$ The magnification of the telescope is $1000$.
$(c)$ The image of the planet is erect and diminished.
$(d)$ The aperture of the eyepiece is smaller than that of the objective.
The correct statements are:

If a telescope is reversed,i.e.,viewed from the objective side,what happens to the appearance of the object?

In normal adjustment,for a refracting telescope,the distance between the objective and the eyepiece is $30\,cm$. The focal length of the objective,when the angular magnification of the telescope is $2$,will be $.....\,cm$.