Microscope
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{{Infobox Laboratory equipment
|name = Microscope
|image = Microscope_de_HOOKE.png|200px
|caption = [[Robert Hooke]]'s microscope
|uses = Small sample observation
|notable_experiments = Discovery of [[Cell (biology)|cell]]s
|inventor = [[Hans Lippershey]]<br/>[[Hans Janssen]]
|related = [[Electron microscope]]
}}
A '''microscope''' ([[Greek language|Greek]]: ''{{polytonic|μικρόν}}'' (''micron'') = small + ''{{polytonic|σκοπεῖν}}'' (''skopein'') = to look at) is an [[instrument]] for viewing objects that are too small to be seen by the naked or unaided [[eye]]. The [[science]] of investigating small objects using such an instrument is called [[microscopy]]. The term ''microscopic'' means minute or very small, not visible with the eye unless aided by a microscope.
==History==
The microscopes used in schools and homes trace their [[history]] back almost 1200 years with [[Abbas Ibn Firnas]]'s corrective lenses,<ref>Dr. Kasem Ajram (1992). Miracle of Islamic Science, Appendix B. Knowledge House Publishers. ISBN 0911119434</ref> and it was [[Ibn al-Haytham]]'s ''Book of Optics'' — which was written when he was under house arrest from [[1011]] to [[1021]] — that laid the foundation for optical technology.<ref>Richard Powers ([[University of Illinois at Urbana-Champaign|University of Illinois]]),[http://online.physics.uiuc.edu/courses/phys199epp/fall06/Powers-NYTimes.pdf Best Idea; Eyes Wide Open], ''[[New York Times]]'', April 18, 1999. (page 4)</ref>
The first useful microscope was made around 1595 in Middleburg, Holland. <ref>[http://nobelprize.org/educational_games/physics/microscopes/timeline/index.html Microscopes: Time Line<!-- Bot generated title -->]</ref> Three different eyeglass makers have been given credit for the invention: [[Hans Lippershey]] (who also developed the first real [[telescope]]); [[Hans Janssen]]; and his son, [[Zacharias Janssen|Zacharias]]. The coining of the name "microscope" has been credited to [[Giovanni Faber]], who gave that name to [[Galileo Galilei]]'s compound microscope in 1625,<ref>Stephen Jay Gould(2000). The Lying Stones of Marrakech, ch.2 "The Sharp-Eyed Lynx, Outfoxed by Nature". London: Jonathon Cape. ISBN 0224050443</ref>. (Galileo had called it the "''occhiolino''" or "''little eye''".)
The most common type of microscope—and the first to be invented—is the [[optical microscope]]. This is an [[optics|optical]] [[measuring instrument|instrument]] containing one or more [[Lens (optics)|lenses]] that produce an enlarged image of an object placed in the focal plane of the lens(es). There are, however, many other microscope designs.
==Types==
[[Image:MicroscopesOverview.svg|thumb|right|300px|Several types of microscopes]]
"Microscopes" can largely be separated into three classes, [[optical]] theory microscopes, electron microscopes and scanning probe microscopes.
Optical theory microscopes are microscopes which function through the [[optical]] theory of lenses in order to magnify the image generated by the passage of a [[wave]] through the sample. The waves used are either [[electromagnetic waves|electromagnetic]] in [[optical microscope]]s or [[electron]] beams in [[electron microscopes]]. The types are the Compound Light, Stereo, and the electron microscope.
===Optical microscopes===
{{main|Optical microscope}}
[[Optical microscope]]s, through their use of visible wavelengths of light, are the simplest and hence most widely used type of microscope.
Optical microscopes use [[refraction|refractive]] lenses, typically of [[glass]] and occasionally of [[plastic]], to focus light into the eye or another light detector. Typical magnification of a light microscope is up to 1500x with a [[angular resolution#Microscope case|theoretical resolution limit]] of around 0.2 [[micrometres]] or 200 [[nanometers]]. Specialised techniques (e.g., [[Confocal laser scanning microscopy|scanning confocal microscopy]]) may exceed this magnification but the resolution is an insurmountable [[diffraction]] limit.
[[Image:CBP checking authenticity of a travel document.jpg|thumb|left|250px|A stereo microscope is often used for lower-power magnification on large subjects.]]
Various [[wavelength]]s of light are sometimes used for special purposes, for example, in the study of biological tissue.<ref>[http://www.truevisionmicroscopes.com/category/products/epi-fluorescence-microscope/ epi-fluorescence-microscopy]</ref> [[Ultraviolet]] light is used to illuminate the object being viewed in order to excite a [[fluorescent]] dye which then emits visible light. [[Infrared]] light is used to study thick slices of biological tissue because infrared light's low diffraction coefficient permits viewing deeper into tissue.
Other microscopes which use [[electromagnetic waves|electromagnetic]] wavelengths not visible to the human eye are often called optical microscopes. The most common of these, due to its high resolution yet no requirement for a [[vacuum]] like electron microscopes, is the [[x-ray microscope]].
===Electron microscopes===
{{main|Electron Microscope}}[[Image:JEOL JSM-6340F.jpg|thumb|Scanning electron microscope, the column, specimen chamber, and signal detectors]]
Electron microscopes, which use beams of [[electron]]s instead of light, are designed for very high magnification usage. Electrons, which can be accelerated to produce a much smaller wavelength than visible light, allow a much higher resolution. The main limitation of the electron beam is that it must pass through a [[vacuum]] as air molecules would otherwise scatter the beam.
Instead of relying on [[refraction]], lenses for [[electron microscope]]s are specially designed electromagnets which generate magnetic fields that are approximately parallel to the direction that electrons travel. The electrons are typically detected by a [[phosphor]] screen, [[photographic film]] or a [[charge-coupled device]] (CCD).
Two major variants of electron microscopes exist:
*[[Scanning electron microscope]]: looks at the surface of bulk objects by scanning the surface with a fine electron beam and measuring reflection. May also be used for [[spectroscopy]].
*[[Transmission electron microscope]]: passes electrons completely through the sample, analogous to [[bright field microscopy|basic optical microscopy]]. This requires careful sample preparation, since electrons are scattered so strongly by most materials.This is a scientific device that allows people to see objects that could normally not be seen by the naked or unaided eye.
===Scanning probe microscope===
In [[scanning probe microscopy]] (SPM), a physical probe is used either in close contact to the sample or nearly touching it. By rastering the probe across the sample, and by measuring the interactions between the sharp tip of the probe and the sample, a [[micrograph]] is generated. The exact nature of the interactions between the probe and the sample determines exactly what kind of SPM is being used. Because this kind of microscopy relies on the interactions between the tip and the sample, it generally only measures information about the surface of the sample.
A variation of the SPM is the SECM ('''S'''canning '''E'''lectro'''C'''hemical '''M'''icroscope). A SECM images a sample in a similar manner as a SPM but the sample is in an electrolyte solution with the SECM using electrochemically active tip<ref>[http://www.msstate.edu/dept/chemistry/dow1/secm/secm.html SECM ('''S'''canning '''E'''lectro'''C'''hemical '''M'''icroscope) - David O. Wipf - Mississippi State University]</ref>.
===Other microscopes===
[[Scanning acoustic microscope]]s use sound waves to measure variations in acoustic impedance. Similar to [[Sonar]] in principle, they are used for such jobs as detecting defects in the subsurfaces of materials including those found in integrated circuits.
==References==
{{Reflist}}
==See also==
[[Image:4microssopes4.jpg|thumb|130px|Different microscopes]]
{{commonscat|Microscopes}}
*[[Acronyms in microscopy]]
*[[Angular resolution]]
*[[Bright field microscopy]]
*[[Condensed Matter Physics]]
*[[Confocal microscopy]]
*[[Dark field microscopy]]
*[[Electron Microscope]]
*[[Fluorescence interference contrast microscopy]]
*[[Fluorescence microscope]]
*[[Microscope image processing]]
*[[Microscopy]]
*[[Optical Microscope]]
*[[Intel Play]]
*[[Phase contrast microscopy]]
*[[Microscope slide]]
*[[Telescope]]
*[[Timeline of microscope technology]]
*[[X-ray microscope]]
*[[b:Botany/Microscopy laboratory|Microscopy laboratory]] in: ''A Study Guide to the Science of Botany'' at Wikibooks
== External links ==
* [http://www.microscopyu.com Nikon MicroscopyU, tutorials from Nikon]
* [http://micro.magnet.fsu.edu/index.html ''Molecular Expressions'' '': Exploring the World of Optics and Microscopy'', Florida State University.]
* [http://www.nature.com/nm/journal/v13/n10/full/nm1007-1128a.html;jsessionid=3E930D2B03F906738970432C43DB516B "'''Microscopes made from bamboo'''" nature.com]
{{Laboratory equipment}}
[[Category:Microscopy|Microscopy]]
[[Category:Microscopes|Microscopes]]
[[Category:Microbiology equipment]]
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