The intermediate image formed by the objective of a compound microscope is

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?......$mm$

The magnifying power of a simple microscope can be increased if we use an eyepiece of:

In a Ramsden eyepiece,two planoconvex lenses,each of focal length $f$,are separated by a distance of $12 \ cm$. The equivalent focal length (in $cm$) of the eyepiece is:

$A$ compound microscope has a magnifying power of $30$. The focal length of its eyepiece is $5 \ cm$. Assuming the final image is at the least distance of distinct vision $(25 \ cm)$,the magnification produced by the objective is:

If the focal length of the objective lens and the eye lens are $4 \, mm$ and $25 \, mm$ respectively in a compound microscope,and the length of the tube is $16 \, cm$,find its magnifying power for the relaxed eye position.