The large aperture of an astronomical telescope is used to:

The magnifying power of an astronomical telescope for normal adjustment is given by:

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:

What is the angular magnification of a telescope if the focal lengths of the objective and eye lenses are $10 \ cm$ and $10 \ mm$ respectively,and the tube length is $11 \ cm$?

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

The objective lens of a telescope has a focal length of $100 \, cm$. When the final image is formed at the least distance of distinct vision,the distance between the lenses is $105 \, cm$. Calculate the focal length of the eyepiece in $cm$.