Simple Microscope
It is used for observing magnified images of objects. It is consists of a converging lens of small focal length.
Magnifying Power
( i) When final image is formed at least distance of distinct vision( D), then M = 1 + d / f where, f = focal length of the lens.( ii) When final image is formed at infinity, then M = D / f
Compound Microscope
It is a combination of two convex lenses called objective lens and eye piece separated by a distance. Both lenses are of small focal lengths but f o < f e, where f o and f e are focal lengths of objective lens and eye piece respectively