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Essay on microscopy. There are two types of electron microscope, transmission and scanning microscopes.

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Electron Microscopy There are two types f electron microscope, transmission and scanning microscopes. The transmission electron microscope produces sharp definition at low magnification, as it presents a 2D image whereas the scanning electron microscope does not have such high resolving power but gives a three-dimensional effect showing surface detail. An electron microscope is preferred over a light microscope since it has the ability to produce higher magnification, which increases the amount of visible detail, as well as higher resolution, since increasing the resolving power of a microscope depends on the wavelength of the electromagnetic radiation used. Therefore an electron beam is used resulting in a smaller wavelength is needed. ...read more.


In other procedures the specimen does not have to be cut into thin sections but the surface is coated with a thin film of gold, The tissue is soaked in alcohol to dehydrate it Tissue is embedded in a resin which becomes hard. The embedded tissue is cut using a microtome or into very thin sections using a knife made of glass. Very small specimens such as viruses and large molecules do not have to be sectioned. Prior to sectioning and cutting tissue is preserved using substances which prevent enzyme action The general outline for freeze facture technique consists of cells frozen quickly in liquid nitrogen which stops cell components instantly. ...read more.


To do so it uses electromagnets to focus the image onto a fluorescent screen, the specimen can then be viewed via low and high magnification. The specimen can not be a living cell. Electron beams can not pass through glass and likewise can not be used to look at living cells, since the atoms in organic molecules have a low atomic number and so do not scatter electrons. In a scanning electron microscopes an image is emitted or reflected from the surface of a complete specimen. The similarity between a scanning electron microscope and a transmission electron microscope are specimens must be stained in order to improve contrast. Important since a high-intensity electron beam can destroy parts of the specimen, producing light-coloured areas on the screen. ...read more.

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