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Electron Microscopy

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Devesh Parekh

Electron Microscopy

As the curiosity of scientists around the world increased, so did the demand for more advanced technology to meet their demands. The light microscope that had previously been more than sufficient was outdated due to its poor resolution. Photon particles were too large and therefore the resolution of light microscopes was not good enough. When the electron microscope which could look at 2 objects 2 nanometres apart clearly was invented, scientists found it a useful tool in furthering their knowledge of organisms.

There are two types of electron microscopes; the transmission microscope and the scanning microscope. The electron microscope cannot be used to look at living cells. This is because the atoms in organic molecules have a low atomic number so do not scatter electrons and also a high-intensity electron beam can destroy parts of the specimen, producing light coloured areas on the screen.

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The transmission electron microscope allows us to see as separate structures parties which are as close together as 2 nanometres (therefore, the resolution of the transmission electron microscope is about 2 nanometres). The transmission electron microscope can be used at low as well as high magnification. However, it can produce a sharp definition at a low magnification. The electron microscope uses electron magnets to focus the image onto a fluorescent screen. The specimen being looked at must be very thin as electrons must be able to pass through parts of the specimen.

Unlike a transmission electron microscope, a scanning electron scans electron beams to and fro across the surface of a complete specimen to produce a 3-dimensional effect showing surface detail. As a result, the specimen does not have to be cut into thin sections but the surface is still coated with a thin film of gold.

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There are two types of electron microscope and they both have their advantages. The transmission microscope allows us to see inside a cell with great detail and the scanning microscope focuses on surface detail which fives us a 3D view of the specimen. As the transmission microscope relies on rays of electrons being able to pass through the specimen, the specimen must be very thin and special techniques are used to obtain such thin tissue samples.

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