Ernst August Friedrich Ruska
(1906 - 1988)
German electrical engineer who invented the electron microscope. He
was awarded half of the Nobel Prize for Physics in 1986 (the other half
was divided between Heinrich Rohrer and Gerd Binnig).
Ruska studied at the Technical University of Munich during 1925-27 and
then enrolled at the Technical University in Berlin. Around this time
he began the studies that led to his invention of the electron microscope.
The extent to which an optical microscope could resolve the detail of
a highly magnified object was limited by the wavelengths of the light
beams used to view the object. Since it had been established in the
1920s that electrons have the properties of waves about 100,000 times
shorter than those of light, Ruska posited that if electrons could be
focused on an object the same way light is, at extremely high magnifications
the electrons would yield greater detail (i.e., have a greater resolving
power) than would conventional light microscopes. In 1931 he built the
first electron lens, an electromagnet that could focus a beam of electrons
just as a lens focuses a beam of light. By using several such lenses
in a series, he invented the first electron microscope in 1933. In this
instrument, electrons were passed through a very thin slice of the object
under study and were then deflected onto photographic film or onto a
fluorescent screen, producing an image that could be greatly magnified.
Ruska joined Siemens-Reiniger-Werke AG as a research engineer in 1937,
and in 1939 the company brought out its first commercial electron microscope,
which was based on his inventions. Ruska did research at Siemens until
1955 and then served as director of the Institute for Electron Microscopy
of the Fritz Haber Institute from 1955 to 1972. He was also a longtime
professor at the Technical University of West Berlin.