The Compound Microscope
The compound microscope consists of two lenses – the objective lens and the eyepiece lens. The first lens (the objective lens) forms a real magnified image of the object. This real image can then be considered as the object for the eyepiece lens which acts as a magnifying lens.
The rays from this real image form a virtual magnified image after passing through the eyepiece lens.
In normal adjustment the virtual image is arranged to be located at the near point of the eye (about 25cm) so that maximum angular magnification can be achieved.
From the diagram above the magnification due to the objective is
The magnification due to the eyepiece lens is
The overall magnification is the product of these: