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Microscope

Robert Hooke's microscope
Uses Small sample observation
Notable experiments
 Discovery of cells
Inventor Hans Lippershey
Hans Janssen
Related items Electron microscope
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A microscope (Greek: μικρόν (micron) = small + σκοπεῖν (skopein) = to look or see) 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.

Contents

History

See also: History of optics

The microscopes used in schools and homes trace their history back almost 1200 years with Abbas Ibn Firnas's corrective lenses,[1] 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.[2][3]

The first microscope was made around 1595 in Middleburg, Holland. [4] 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. The coining of the name "microscope" has been credited to Giovanni Faber, who gave that name to Galileo Galilei's compound microscope in 1625,[5]. (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 optical instrument containing one or more 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

Several types of microscopes
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 (in optical microscopes) or electron beams (in electron microscopes). The types are the Compound Light, Stereo, and the electron microscope.

Optical microscopes

Main article: Optical microscope

Optical microscopes, through their use of visible wavelengths of light, are the simplest and hence most widely used type of microscope.

Optical microscopes use 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 theoretical resolution limit of around 0.2 micrometres or 200 nanometers. Specialised techniques (e.g., scanning confocal microscopy) may exceed this magnification but the resolution is an insurmountable diffraction limit.

A stereo microscope is often used for lower-power magnification on large subjects.
A stereo microscope is often used for lower-power magnification on large subjects.

Various wavelengths of light are sometimes used for special purposes, for example, in the study of biological tissue.[6] Ultraviolet light is used to illuminate the object being viewed in order to excite a vice (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 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.

If your school is too small to have their own electron microscope, you still might be able to use some "borrowed time" on an electron microscope via Bugscope [7] which is an educational outreach program from the Imaging Technology Group[8] at the Beckman Institute [9].


Other microscopes

Scanning acoustic microscopes 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

  1. ^ Dr. Kasem Ajram (1992). Miracle of Islamic Science, Appendix B. Knowledge House Publishers. ISBN 0911119434
  2. ^ Richard Powers (University of Illinois),Best Idea; Eyes Wide Open, New York Times, April 18, 1999. (page 4)
  3. ^ A short history on the Microscope.
  4. ^ Microscopes: Time Line
  5. ^ Stephen Jay Gould(2000). The Lying Stones of Marrakech, ch.2 "The Sharp-Eyed Lynx, Outfoxed by Nature". London: Jonathon Cape. ISBN 0224050443
  6. ^ epi-fluorescence-microscopy
  7. ^ "Bugscope web page".
  8. ^ "UIUC ITG web page".
  9. ^ "Beckman Institute web page".

See also

Different microscopes
Different microscopes
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