The Transmission Electron Microscope

The transmission electron Microscope (TEM) was the first type of electron microscope to be developed. It was developed by Max Knoll and Ernst Ruska in Germany in 1931. The transmission electron microscope (TEM) operates on the same basic principles as the light microscope but uses electrons instead of light. As mentioned earlier, what you can see with a light microscope is limited by the wavelength of light. TEMs use electrons as a "light source" and their much lower wavelength makes it possible to get a resolution a thousand times better than with a light microscope. The enlarged version of the image of the specimen appears on a fluorescent screen or in a layer of photographic film.

You can see objects to the order of .2 nanometers. For example, you can observe and study small details in the cell or other different materials down to near atomic levels. The microscope's high magnification range and resolution has made the TEM a valuable tool in medical, biological, and materials research.

Transmission electron microscopy has had an important impact on the knowledge and understanding of viruses and bacteria. The improvement in resolution provided by electron microscopy has allowed visualization of viruses as the causes of transmissible infectious disease. Researchers are continuing the use of electron microscopy in the investigation of such pathogens as SARS and the human monkeypox virus. SARS is a severe acute respiratory disease in humans which is caused by the SARS virus. Monkeypox is a rare smallpox-like disease that is most common in the rain forests of central and West Africa.

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