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The electron microscope has become one of the most widely utilized instruments for materials characterization. An electron microscope is a scientific instrument that allows us to "see" objects so small that they cannot be seen in any other way. (CITE) Electron microscopes have allowed scientists to see individual molecules and atoms for the first time. Most microscopes, including those in schools and laboratories today, are optical microscopes. They use glass lenses to enlarge, or magnify, an image. An optical microscope cannot produce an image of an object smaller than the length of the light wave in use. To see anything smaller than 2, 000 angstroms (about 1 / 250, 000 of an inch) a wave of shorter length would have to be used.
In 1923, a French physicist Louis de Broglie suggested that electrons, like light, travel in a wave. In addition, the wavelength of electrons is much shorter than the wavelength of light. An electron is an elementary particle carrying a unit of charge of negative electricity. (CITE) J. J. Thompson discovered the electron in 1897 while showing what cathode rays were composed of. (CITE) The first time that the electron was used for a unit of negative electricity was in the late 19 th century by the English physicist G. J.
Stoney. The electron is the lightest particle having a non-zero rest mass. Electrons also have a wavelike property, which made them prime candidates for microscopes and other devices. Yarbrough 2 Ernst Ruska (1906 - 1988), a German physicist, used De Broglie's discovery to design a microscope that used an electron beam instead of light to produce an image. (CITE) By 1931, with the help of partner Dr. Max Knoll Ruska had produced a working model of the first electron microscope. Several types of electron microscopes have been developed since Ruska's first model.
Some are so large that they are housed in silos several stories high while others are small enough to fit in the palm of a hand. These instruments have given scientists a new look at the world around us. Ruska's working model was a transmission electron microscope (TEM). It sends a beam of electrons, rather than light, through the object being viewed. The object to be viewed must be very thin so the electrons can pass through it. Because air is too dense for electrons to pass through, the object must be placed in a vacuum chamber.
A beam of electrons is then focused on the object. Magnetic lenses that act in the same way as glass lenses in an optical microscope spread the part of the beam that passes through the object. Finally, the beam strikes a fluorescent screen. The magnified image of the object can be seen on the screen of a television-like monitor. The images formed by a transmission electron microscope are black and white like an X-ray picture. Computers can be used to translate the image information into a three-dimensional colored image.
In 1970, another electron microscope called the scanning electron microscope (SEM) was developed. The scanning electron microscope is used to study the smallest Yarbrough 3 details on the surface of an object. It sees surfaces as your eyes do. The images, which are sharp and clear, look like three-dimensional photographs. An extremely fine beam of electrons is focused on the object. The beam travels, or scans, back and forth across the object from side to side knocking loose a shower of electrons.
The ones knocked loose are caught by a collector and used to form an image on a television-like monitor. In 1981, fifty years after the first electron microscope was designed, the scanning tunneling microscope (STM). The STM detects the smallest surface details of an object. With the STM, scientists can examine the structure and properties of individual atoms. The inventors of the scanning tunneling electron microscope shared the 1986 Nobel Prize in physics with Ernst Ruska, the designer of the first electron microscope. The electron microscope, only the fourth invention ever to have received the award, was called "one of the most important inventions of this century. " Scientists and researchers are finding many new uses for these powerful microscopes.
As biologists get a closer look at how the body works and what happens when diseases attack, new treatments can be developed. Dr. Ming Chen, a professor at the University of Alberta, got to study rice diseases that could be caused by viruses while an undergraduate in Taiwan. Because Dr. Chen did not have an electron microscope at the time, he had a hard time proving it. (CITE) In addition, if it there was not an electron microscope the AIDS virus would have never been discovered.
Engineers examine metals and other materials to find new ways to make them stronger and longer lasting. In addition, when the smallest parts of computers and other electronic products are viewed, defects can be found and new manufacturing techniques are developed. Dr. Jim Quinn has been quoted saying, "Without the TEM or SEM you would not have microchips... 486, Pentium, G 3, K 6, etc... computers. Hence, we would not have the society we presently enjoy. " (CITE) Each day there are more discoveries and surprises as the once invisible world emerges.
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Research essay sample on Electron Microscope Three Dimensional
