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FutureStarrParts of a microscope
A microscope is a scientific instrument designed to view very small objects, like cells, in very close detail. Its main purpose is to magnify images of objects 10,000 times their actual size, meaning that a lot of things can be seen that can’t be seen without magnification.This is similar to the ordinary light microscope; however, the condenser system is modified so that the specimen is not illuminated directly. The con-denser directs the light obliquely so that the light is deflected or scattered from the spec-imen, which then appears bright against a dark background. Living specimens may be observed more readily with darkfield than with brightfield microscopy.
This microscope is used most frequently to visualize speci-mens that are chemically tagged with a fluorescent dye. The source of illumination is an ultraviolet (UV) light obtained from a high-pressure mercury lamp or hydrogen quartz lamp. The ocular lens is fitted with a filter that permits the longer ultraviolet wavelengths to pass, while the shorter wavelengths are blocked or eliminated. Ultraviolet radiations are absorbed by the fluorescent label and the energy is re-emitted in the form of a different wavelength in the visible light range. The fluorescent dyes absorb at wavelengths between 230 and 350 nanometers (nm) and emit orange, yellow, or greenish light. This microscope is used primarily for the detection of antigen-antibody reactions. Antibodies are conjugated with a fluorescent dye that becomes excited in the presence of ultraviolet light, and the fluorescent portion of the dye becomes visible against a black background.
Transmission electron microscopes require speci-mens that are thinly prepared, fixed, and dehydrated for the electron beam to pass freely through them. As the electrons pass through the specimen, images are formed by direct-ing the electrons onto photographic film, thus making internal cellular structures visi-ble. Scanning electron microscopes are used for visualizing surface characteristics rather than intracellular structures A narrow beam of electrons scans back and forth, producing a three-dimensional image as the electrons are reflected off the specimen's surface.While scientists have a variety of optical instruments with which to perform routine laboratory procedures and sophisticated research, the compound brightfield micro-scope is the "workhorse" and is commonly found in all biological laboratories. Although you should be familiar with the basic principles of microscopy, you probably have not been exposed to this diverse array of complex and expensive equipment. Therefore, only the compound brightfield microscope will be discussed in depth and used to examine specimens. (Source: www2.hawaii.edu)
Although magnification is important, you must be aware that unlimited enlargement is not possible by merely increasing the magnifying power of the lenses or by using additional lenses, because lenses are limited by a property called resolving power. By definition, resolving power is the ability of a lens to show two adjacent objects as discrete entities. When a lens cannot discriminate, that is, when the two objects appear as one, it has lost resolu-tion. Increased magnification will not rectify the loss, and will, in fact, blur the object. The resolv-ing power of a lens is dependent on the wave-length of light used and the numerical aperture, which is a characteristic of each lens and imprinted on each objective. The numerical aper-ture is defined as a function of the diameter of the objective lens in relation to its focal length. It is doubled by use of the substage condenser; which illuminates the object with rays of light that pass through the specimen obliquely as well as directly.
Real and magnified images of minuscule particles or objects can be achieved using a combination of lenses. A compound microscope is an intricate gathering of a combination of lenses that renders a highly maximized and magnified image of microscopic living entities and other complex details or tissues and cells.There are organisms and other objects in the world that are just too small for the naked eye to see. These tiny organisms are called microorganisms. When scientists need to view these tiny organisms, then they use a compound microscope, also called a compound light microscope. What is a compound microscope? The definition of a compound microscope is "an upright microscope that utilizes two different lenses to magnify the size of the objects being viewed." The name itself describes what it is. The tern compound means to add to it, light refers to the light that is used in the microscope, and microscope means to view tiny things. So, a compound microscope adds the two lenses together to magnify tiny objects.(Source:study.com)