An object is clearly seen through an astronomical telescope of length $50 \ cm$. The focal lengths of its objective and eyepiece,respectively,can be

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

The focal length of the objective lens of a telescope is $30 \text{ cm}$ and that of its eye lens is $3 \text{ cm}$. It is focused on a scale at a distance $2 \text{ m}$ from it. The distance of the objective lens from the eye lens to see the clear image is: (in $\text{ cm}$)

$A$ giant refracting telescope at an observatory has an objective lens of focal length $15 \, m$. If an eyepiece of focal length $1.0 \, cm$ is used,what is the angular magnification of the telescope?

To produce a magnified erect image of a far object,along with a convex lens,we will require:

The objective and eyepiece of an astronomical telescope are double convex lenses with refractive index $1.5$. When the telescope is adjusted to infinity,the separation between the two lenses is $16 \,cm$. If the space between the lenses is now filled with water and the telescope is again adjusted for infinity,then the present separation between the lenses is: (in $\,cm$)