Editing Optical microscope (section)

===Compound microscope===
[[File:Compound microscope geometric optics.svg|thumb|left|400px|Ray optics diagram of a compound microscope.]]

A compound microscope uses a lens close to the object being viewed to collect light (called the [[Objective (optics)|objective]] lens), which focuses a [[real image]] of the object inside the microscope. That image is then magnified by a second lens or group of lenses (called the [[eyepiece]]) that gives the viewer an enlarged inverted virtual image of the object. <ref name=Watt>{{cite book|author=Ian M. Watt|title=The Principles and Practice of Electron Microscopy|url=https://books.google.com/books?id=Y6-sE4gUX-QC&pg=PA6|year=1997|publisher=Cambridge University Press|isbn=978-0-521-43591-8|page=6}}</ref> 

The use of a compound objective-eyepiece combination allows for much higher angular magnification:
For an object of height <math>h</math>,
it can at most occupy an unmagnified [[angular size]] <math>\theta_0 = h / d_0</math> while remaining in focus,
achieved when it is placed at the [[Near point|near point distance]] <math> d_0 </math> of the eye (about 11 cm).
The virtual image created by the compound microscope achieves an angular size of
<math> \theta = -h s /f_\text{objective}f_\text{eyepiece}</math>,
where <math> s</math> is the distance between the neighboring objective and eyepiece focal points.
This is an angular magnification of <math>\theta/\theta_0 = -s d_0 /f_\text{objective}f_\text{eyepiece}</math>.

Common compound microscopes often feature exchangeable objective lenses, allowing the user to quickly adjust the magnification.<ref name=Watt/> A compound microscope also enables more advanced illumination setups, such as [[phase contrast]].{{cn|date=December 2024}}