Two convex lenses of focal lengths $0.3 \, m$ and $0.05 \, m$ are used to make a telescope. The distance kept between the two is .... $m$

An astronomical telescope has a magnifying power $10$. The focal length of the eyepiece is $20 \, cm$. The focal length of the objective is.....$cm$.

In an astronomical telescope in normal adjustment,a straight black line of length $L$ is drawn on the objective lens. The eyepiece forms a real image of this line. The length of this image is $l$. The magnification of the telescope is

The length of a telescope is $36 \ cm$. The focal lengths of its lenses can be

$A$ telescope has an objective of focal length $50 \text{ cm}$ and an eyepiece of focal length $5 \text{ cm}$. The least distance of distinct vision is $25 \text{ cm}$. The telescope is focused for distinct vision on a scale $200 \text{ cm}$ away. The separation between the objective and the eyepiece is.......$\text{cm}$.

$A$ telescope has an objective lens of focal length $200 \, cm$ and an eyepiece with focal length $2 \, cm$. If this telescope is used to see a $50 \, m$ tall building at a distance of $2 \, km$,what is the height of the image of the building formed by the objective lens in $cm$?