When a telescope is adjusted for parallel light,the distance of the objective from the eyepiece is found to be $80 \,cm$. The magnifying power of the telescope is $19$. The focal lengths of the lenses are

When the tube length of an astronomical telescope is increased,its magnifying power will .......

For a telescope,the focal length of the objective lens is $15\, cm$ and the focal length of the eyepiece is $10\, mm$. If the tube length is $16\, cm$,find the magnification.

The focal lengths of the objective and eyepiece of an astronomical telescope are $60\, cm$ and $5\, cm$ respectively. When the final image is formed at the least distance of distinct vision $(25\, cm)$, the magnifying power and the length of the telescope will be, respectively:

The diameter of the moon is $3.5 \times 10^3 \, km$ and its distance from the Earth is $3.8 \times 10^5 \, km$. Find the angle subtended by the moon at the eye when viewed through a telescope. The focal length of the telescope's objective is $4 \, m$ and the focal length of the eyepiece is $10 \, cm$. The angle is .......... $^o$.

On which of the following does the magnifying power of a telescope depend?