Teaching The Important Uses Of The Electron Microscope
Unlike conventional microscopy, the electron microscope can provide excellent images in very high magnifications. Usually, the problem with traditional light microscopy is that the images produced are not very effective for proper observation or inspection. Since it was first introduced in the 30s, the electron microscope has allowed scientists, explorers and researchers to view a specimen’s surface and structure at microscopic levels. The electron microscope is also one of the best and most effective tools to use for teaching.
Teaching the concept of the electron microscope Students of science and those interested in microscopic research will find the electron microscope a very fascinating and useful instrument. As an introduction to this type of microscopy, it is best that the principle that explains how the microscope works is taught first.
The electron microscope is unique in that it does not use visible light to illuminate and magnify the image of the specimen. Instead, it uses electrons. Electrons are the component of atoms that are negatively charged. These particles are found in the atoms’ outer layers. Like neutrons and protons, electrons are called elementary particles – the smallest components of matter that can be isolated.
How electrons work with electron microscopy Electrons perform significant activities that characterize many chemical and physical properties of known matter. One of these is by producing light and electricity. Computers, lamps and flashlights, for example, depend on electrons and their movement in order to work. To produce light, electrons located in the outermost layers of an atom lose energy. This energy is transformed to another form of energy, which is light. This characteristic of the electron is being maximized in microscopy, specifically in the type that is eponymous to this particle.
To understand how electrons are used to magnify images of specimens, it would be better to compare electron microscopy to conventional light microscopy. With regular microscopes which use visible light, structures in a specimen can only be viewed if they are larger compared to the length of the light waves that hit them. The light waves that are bounced back through the objective lens and on through the eyepiece may then be observed.
Electrons have a shorter wavelength compared to light. Using an electron source, an electron stream is produced and pushed toward the object being observed. Interactions happen within the specimen and affect the beam of electrons. The microscope then detects the effects of these interactions and transforms them into a highly magnified image. Electron microscopy can be used to view samples made of conductive and semi-conductive substances, such as steel or gold.
High magnifications achieved using the electron microscope Conventional microscopy using visible light is only capable of magnifications of up to 1000x or 2000x. With an electron microscope, images of objects may be magnified nearly 1 million times. The electron microscope also uses electromagnetic and electrostatic lenses instead of glass lenses to illuminate and produce the image of the specimen.
Types of electron microscopes There are two major types of electron microscopes – the TEM or transmission electron microscope and the SEM or scanning electron microscope. The TEM was the first type of electron microscopy developed. Using high-voltage electron beams, electrons are focused onto a specimen and bounced back, carrying information regarding the inner components or structure of the object. The image is magnified by electromagnetic lenses and forwarded through the eyepiece, a CCD camera or a photographic plate. Whatever image is seen using the TEM will be viewed in real time. It is also capable of producing higher resolution images compared to the SEM.
The scanning electron microscope or SEM does not make use of high voltage electron beams. Instead, it magnifies images of a specimen through detection of secondary electrons emitted from the scanned horizontally across the specimen in order to produce a highly magnified image. SEM produces this image based on what the beam processes on the specimen’s surface instead of using transmission.
When using the SEM, it is necessary to prepare the sample in a vacuum. This is to avoid a burn out when electrons mix with gas molecules. Although an image may still be produced, it will appear as a low quality picture.
The SEM is the type of electron microscopy that is often used to process image samples in bulk. Compared to TEM, it also offers a better depth of view. Samples viewed using the SEM also do not have to be sliced thinly.
What fields of study benefit from electron microscopes? The concept and use of the electron microscope is taught in many science subjects. It is also a mainstay in many fields of study and research, such as medicine, chemistry, forensics, metallurgy, entomology, physics and biology.
The uses of electron microscopy Electron microscopes are not always required for use in all fields of study. However, if the purpose is to magnify the image of an object beyond 1000x or 2000x, this type of microscopy should be utilized. The electron microscope is also the best instrument to use to view samples such as insects, metals, ceramics and plastics. It is also one of the most useful instruments for use in research regarding both organic and inorganic substances, capable of processing the images of specimens such as human and animal cells and tissues and microorganisms such as viruses and bacteria. The electron microscope can also be used to produce nearly three-dimensional images of extremely minute structures better than conventional microscopy.
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