$A$ small telescope has an objective lens of focal length $140\, cm$ and an eyepiece of focal length $5.0\, cm$. What is the magnifying power of the telescope for viewing distant objects when the telescope is in normal adjustment?

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

The magnifying power of an astronomical telescope in the normal adjustment position is $100$. The distance between the objective and the eye piece is $101 \,cm$. Find the focal length of the objective lens in $cm$.

An observer looks at a tree of height $15 \ m$ with a telescope of magnifying power $10$. To him,the tree appears

What is the primary purpose of the eyepiece in a telescope?

An astronomical telescope has an objective of focal length $100 \, cm$ and an eyepiece of focal length $5 \, cm$. The final image of a star is seen $25 \, cm$ from the eyepiece. The magnifying power of the telescope is ...........