We wish to make a microscope with the help of two positive lenses,both with a focal length of $20\, mm$ each,and the object is positioned $25\, mm$ from the objective lens. How far apart should the lenses be so that the final image is formed at infinity?......$mm$

In a compound microscope,the magnified virtual image is formed at a distance of $25 \, cm$ from the eye-piece. The focal length of its objective lens is $1 \, cm$. If the magnification is $100$ and the tube length of the microscope is $20 \, cm$,then the focal length of the eye-piece lens (in $cm$) is

The objective of a compound microscope is essentially

$A$ wire mesh consisting of very small squares is viewed at a distance of $8 \, cm$ through a magnifying converging lens of focal length $10 \, cm$,kept close to the eye. The magnification produced by the lens is

An angular magnification (magnifying power) of $30X$ is desired using an objective of focal length $1.25 \, cm$ and an eyepiece of focal length $5 \, cm$. How will you set up the compound microscope?

$A$ convex lens of focal length $12.5 \ cm$ is used as a simple microscope. When the image is formed at infinity,the magnification is . . . . . . . (Near point for normal vision is $25 \ cm$)