More about Microscopes
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Microscopes are instruments used to study minute objects. Although optical microscopes are the most widely used, other types of microscopes, such as electron and x-ray microscopes, allow researchers to view even smaller objects. In fact, an object viewed through an electron microscope can be magnified millions of times. However, due to their method of operation and to the preparation required for viewing samples, electron microscopes present a variety of complications when viewing certain objects, especially those of a biological nature.
Most microscopic research is performed using compound optical microscopes. These microscopes, which can provide magnification of up to one thousand times the original image, involve a series of lenses, including an eye-piece and different adjustable objective lenses. The object being viewed is placed beneath the active objective lens on an area called a stage. Generally, light is directed at the object from a light source below the stage. The lenses, which are precisely calibrated, high-quality glass shapes, then magnify the image and direct it through the eyepiece for viewing.
Electron microscopes are used to examine cells, large molecules and other objects too small to be properly studied with an optical microscope. These devices use a beam of electrons to determine the microscopic structure of the object being studied. In the most basic form of electron microscope, the transmission electron microscope, this beam is sent through the specimen, magnified, and then directed to a photographic plate or other instrumentation, resulting in an image. Other types of electron microscopes include reflection, scanning and scanning transmission.
In many cases, specimens viewed through a microscope are stained or treated with various substances to provide a better image. Although this can alter the object being studied, it may be necessary and generally offers numerous advantages. In fluorescence microscopy, for example, which uses ultraviolet light to study various subjects, dyes can help isolate different cells and cellular structures.