They can refer to the article published in the December 2006 Science Teacher, or email me at: [email protected]
Several different types of electron microscopes exist. Two major ones include the transmission electron microscopy (TEM) and the scanning electron microscopy (SEM). Electron microscopes use electron beams instead of visible light, enabling resolution of features down to a few nanometers.
Electron microscopes use a beam of high-energy electrons to probe the sample. Electron microscopes are scientific instruments that use a beam of highly energetic electrons to examine objects on a very fine scale. High quality electron microscopes can cost from $250,000 to $1,000,000. They are one of the most useful instruments in laboratories.
A scanning electron microscope (SEM) can analyze materials for information about topography, chemical composition, contamination, grain size and thickness with far greater depth of field than is possible with optical microscopy. The depth of field basically means how clear a three-dimensional image looks.
The topography information analyzed by the SEM includes the surface features of an object such as its texture and hardness. A microscope operator can observe the shape and size of the grain particles making up the object and notice if there is any contamination. The composition data includes the elements and compounds that the object is composed of. How the atoms are arranged in the pattern of the object can be detected by the crystallographic. The pattern in the crystal is formed by the way the atoms in a solid material are connected to one another.
In the 1870s, a man named Ernst Abbe explained why the resolution of a microscope is limited. He said that since the microscope uses visible
^ Measuring Electrical Properties with an Electron Force Microscope. Professor Wendy Crone, Madison Metropolitan School District. http://mrsec.wisc.edu/ Edetc/cineplex/MMSD/scanning3.html light and visible light has a set range of wavelengths, the microscope can't produce the image of an object that is smaller than the length of the light wave.
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