If an astronomical telescope has objective and eye-piece focal lengths of $200 \; cm$ and $4 \; cm$ respectively,then the magnifying power of the telescope for normal vision is:

$A$ planet is observed by an astronomical refracting telescope having an objective of focal length $16 \, m$ and an eye-piece of focal length $2 \, cm$. Which of the following statements is correct?

In a reflecting telescope,a secondary mirror is used to:

The relative difference between the focal lengths of the objective and the eye lens in a microscope and a telescope is given as:

The angular magnification of an astronomical telescope is $10$. The final image is formed at infinity. The length of the telescope is $44 \, cm$. The focal length of the objective lens is .......... $cm$.

$A$ small object is placed at a distance of $4 \,m$ from the objective of a telescope of focal length $2 \,m$. The focal length of the eyepiece is $0.2 \,m$. The final image of the object