Electronic microscopy is the use of electrons to produce a magnified image of a specimen. This is conducted via an electron microscope, which uses a beam of electrons as the main source of illumination. Compared to a light-based microscope, an electron microscope has better resolution than an optical microscope that uses light. This is because the wavelengths of electrons are around 100,000 times shorter than those of light photons; thus, they are able to attain greater than 50 pm resolution and can magnify an image up to 10,000,000 times. You can also see the structure of a nanomaterial like graphene (see the Graphene Virtual Microscope app in FreApp.com for more information) Ordinary light microscopes, on the other hand, can only achieve up to 200 nm resolution and can only magnify an image up to 2000 times. For this reason, electron microscopy is deemed as a more advanced microscopic procedure.
Electronic microscopy comes in many different types, depending on the equipment in use. The common equipment used are:
- Transmission electron microscope
- Scanning electron microscope
- Reflection electron microscope
- Scanning transmission electron microscope
- Low-voltage electron microscope
A Brief History
The first electronic microscopy equipment was developed back in 1926 by Hans Busch, but the first prototype was constructed in 1931 by German physicist Ernst Ruska and electrical engineer Max Knoll. The microscope was capable of 400-power magnification. In 1933, Ruska again built another model that exceeded the resolution that an optical lens microscope can achieve. However, the patent for the electron microscope went to Reinhold Rudenberg in May of 1931, when an illness in his family prompted him to create an electrostatic microscope to make the poliomyelitis virus visible.
In 1932, Siemens & Halske built a prototype electron microscope and later on financed the work of Ernst Ruska and Bodo von Borries. Together with Helmut Ruska, they were able to develop applications for the microscope.
Despite these developments, it was only in 1938 that the first practical electron microscope was constructed. The first commercial version then followed in 1939.
Today, electronic microscopy has advanced significantly. The most modern microscopes can provide up to 2-million-power magnification. Nevertheless, they are still based on the prototype that Ruska created many years ago.
Some Disadvantages of Electronic Microscopy
Electronic microscopy is not without its disadvantages, primary of which is the cost of building and maintaining one. Microscopes that are meant to produce high resolution images need to be kept in stable buildings, sometimes even underground ones, and have to be supported by special equipment such as a magnetic field cancelling system. Also, the samples have to be viewed in vacuum; otherwise the molecules that comprise them will scatter their electrons.
Despite these, it is undeniable that electronic microscopy has a major role due to their unique ability to provide high-resolution magnifications.