![]() The specimen is illuminated by a beam oftungsten light focused on it by a sub-stage lens called a condenser,and the result is that the specimen appears dark against a brightbackground. This instrument contains two lens systems for magnifyingspecimens: the ocular lens in the eyepiece and the objective lenslocated in the nose-piece. Electron microscopes use elec-tron beams instead of lightrays, and magnets instead of lenses to observe submicro-scopicparticles.Įssential Features of Various Microscopes Fluorescentmicro-scopes use ultraviolet radiations whose wavelengths are shorterthan those of visible light and are not directly perceptible to thehuman eye. They include brightfield,darkfield, phase-contrast, and fluorescent instruments. The former use visible light orultraviolet rays to illuminate specimens. Microscopes are designated as either lightmicroscopes or electron microscopes. ![]() Over the years, microscopes have evolved from the simple,single-lens instrument of Leeuwenhoek, with a magnification of 300,to the present-day electron microscopes capable of magnificationsgreater than 250,000. In 1673, with the aid of a crude microscopeconsisting of a biconcave lens enclosed in two metal plates,Leeuwenhoek introduced the world to the existence of microbial formsof life. Microbiology, the branch of science that has so vastly extendedand expanded our knowledge of the living world, owes its existence toAntony van Leeuwenhoek. and Sherman, N., Benjamin/CummingsScience Publishing.)ġ.To become familiar with the history and diversity of microscopeinstruments.Ģ.To understand the components, use, and care of the compoundbrightfield microscope.ģ.To learn the correct use of the microscope for observation andmeasurement of microorganisms. (This passage was adapted from Microbiology: A Laboratory Manual,5th edition, Cappuccino, J.S.
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