The regular microscope used in most laboratories is called a compound microscope. It contains two different lenses and uses a focused beam of light to view a specimen. The ocular lens is the one closest to the eye and the objective lens is the one closest to the specimen. The base of the compound microscope contains a condenser for condensing light rays which can be adjusted and controlled by a diaphragm on the condenser. It is one type of light microscope, and most models have a magnification range of 10x to 400x. The maximum magnification for a compound microscope is 2,000x.
The fluorescent microscope is another advanced type of light microscope that uses ultraviolet light as a light source. The ultraviolet light hits the object, causing the electrons in the object to give off light in various shades and colors. The ultraviolet light also causes the resolution of the object to increase. Fluorescent microscopes are useful for identifying bacteria strains and for the analysis of cell structure at a molecular level. The confocal microscope is an advanced form of fluorescent microscope used in molecular biology and good for identifying proteins.
The electron microscope uses a focused beam of electrons instead of a beam of light which increases the resolution even more than the fluorescent microscope, enabling scientists to view specimens that are too small to be visible with a compound microscope. Large molecules are visible with an electron microscope as are viruses which are extremely minute. The beams of electrons travel within in a vacuum and are directed towards the specimen with magnets. The image is projected onto a monitor. Electron microscopes magnify from 200x to 10,000x.
The transmission electron microscope (TEM) works rather like a slide projector and also uses a wire grid onto which very thin slices of the specimen are placed for viewing. It is used for exploring microorganisms and viruses. The specimen is coated with gold or palladium which deflects the beam of electrons, allowing both dark and light areas of the specimen to be viewed. The transmission electron microscope is used in molecular biology and DNA investigation.
The scanning electron microscope is a more contemporary form of the electron microscope developed in the 1980s, allowing three-dimensional viewing of a specimen. For this reason it is a popular microscope for modern science because whole microorganisms can be easily viewed. It also uses gold or palladium staining for clarity. The atomic force microscope is a later version of the scanning electron microscope.