What is an Electron Microscope?
The development of the Scanning Electron Microscope in the early 1950’s brought with it new areas of study in the medical and physical sciences because it allowed examination of a great variety of specimens. As in any microscope the main objective is for magnification and focus for clarity. An optical microscope uses lenses to bend the light waves and the lenses are adjusted for focus. In the SEM, electromagnets are used to bend an electron beam which is used to produce the image on a screen. By using electromagnets an observer can have more control in how much magnification he/she obtains. The electron beam also provides greater clarity in the image produced.
A microscope is very similar to a telescope or, for that matter, a pair of eye glasses. All microscopes, telescopes, and glasses have something in common – lenses. A lens is usually made out of glass and it takes light and bends it so that we can see things more clearly. In glasses, the lenses will bend the light so that things that appear “fuzzy” are brought into focus. In telescopes, lenses take things that are far away and make them appear as if they are close to us so we can see them better. In microscopes, lenses take things that are very small and magnify them so they become visible.
An electron microscope is a type of microscope that uses electrons rather than photons — as a conventional light microscope does — for imaging. Because electrons have a much smaller wavelength than photons, they provide much greater magnification. Electrons are the tiny “satellites” that orbit the atomic nucleus and carry electric charge – these particles are so small that in physics they are often modeled as points. Yet light waves are much larger, with a wavelength of around 500 nanometers for the color green, for instance. The best optical microscopes only offer about 2000X magnification of a sample, whereas some electron microscopes can magnify a sample by 50 million times; in contrast, 2 million times is more typical. This works out to a resolution limit of about 0.1 nanometers, allowing the observation of individual atoms on a surface. The electron microscope was invented in 1931, when the first working prototype was built by Ernst Ruska and Max Knoll. Ruska was eventually awarde
Invented by a German physicist named Ernst Ruska, electron microscopes are mostly used in archaeology, medicine, and geology to look at surfaces or layers of objecs. Rather than using light, electron microscopes use electrons to produce images. They have high resolution and can magnify in small detail.
When thinking about a microscope, you might want to compare it to a telescope, or even something as simple as a pair of glasses. Microscopes, telescopes, and glasses all have one thing in common – lenses. A lens is usually made out of glass and it takes light and bends it so that we can see things more clearly. In glasses, the lenses will bend the light so that things that appear “fuzzy” are brought into focus. In telescopes, lenses take things that are far away and make them appear as if they are close to us so we can see them better. In microscopes, lenses take things that are very small and magnify them so they become visible. Light microscopes are used in a number of areas such as medicine, science, and engineering. However, light microscopes can not give us the high magnifications needed to see the tiniest objects like atoms. For this, we have to use electrons rather than light. Electrons are small particles within the atom. Microscopes that use electrons rather than light are cal
