The number of lenses in a terrestrial telescope is

An observer looks at a distant tree of height $10 \ m$ with a telescope of magnifying power of $20$. To the observer,the tree appears:

In a simple telescope,the focal length of the objective lens is $f_o = 60 \ cm$ and the focal length of the eyepiece is $f_e = 5 \ cm$. If the rays coming from the object make an angle of $2^\circ$ at the objective,then the angular magnification (angular size of the image) is ........... $^\circ$.

The diameter of the moon is $3.5 \times 10^3 \text{ km}$ and its distance from the earth is $3.8 \times 10^5 \text{ km}$. If it is seen through a telescope whose focal lengths for the objective and eye lens are $4 \text{ m}$ and $10 \text{ cm}$ respectively,then the angle subtended by the moon on the eye will be approximately.......$^o$

An astronomical telescope has an angular magnification of magnitude $5$ for distant objects. The separation between the objective and eyepiece is $36 \, cm$ and the final image is formed at infinity. The focal lengths of the objective and eyepiece are respectively:

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 $\text{ cm}$)