Electron microscopes are extremely sophisticated types of magnification devices. These are used in archaeology, medicine, and geology to look at surfaces and layers of objecs such as organs and rocks. Instead of using light, these devices point a stream of electrons at the specimen and attached computers analyze how the electrons are scattered by the material. The specimen must be suspended within a vacuum chamber. With transmission electron microscopes, a scientist gets a view of 2-D slices of the object at different depths. Of course, with such powerful instruments, both the degree of magnification and the resolution, or sharpness of the image, are very high. Scanning electron microscopes are slightly different in that they scan a gold-plated specimen to give a 3-D view of the surface of an object. This view is in black and white, yet gives an amazing picture of, for example, the minute hills and valleys of a dinosaur bone.
A confocal microscope is a step down from the previous types. It uses a laser beam to illuminate a specimen whose image is then digitally enhanced for viewing on a computer monitor. The specimen is often dyed a bright color so the laser gives a more contrasting image. It is mounted on a glass slide just like in high school biology. Confocal microscopes are controlled automatically, and motorized mirrors help with auto-focus.
Two Electron Microscopes are the Scanning Electron Microscope and the Transmission Electron Microscope. Two major variants of electron microscope: 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. It can also obtain detailed information on the sample’s crystallography through selected area diffraction.



July 21st, 2010 at 3:43 am
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