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Ruska, Ernst August Friedrich

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(1906–88) German physicist: pioneer in development of the transmission electron microscope.

The electron microscope has had such a revolutionary effect in science (especially biology) that it must rank with the telescope, optical microscope and spectroscope as an outstanding device. Like these devices it has no universally agreed single discoverer; claims and counter-claims have been made, but the award of a Nobel Prize to Ruska in 1986 for the discovery makes him a central figure.

He studied high voltage and vacuum methods in Munich and Berlin, the appropriate background for his pioneer work on electron optics. By the mid-1920s it was known that electrons could behave not only as particles but, in appropriate experiments, as waves; and H Busch found that a magnetic coil could focus a beam of electrons, rather as a convex lens could focus a light beam. In 1928 M Kroll and Ruska (then a research student in Berlin) made a microscope giving 17×magnification using these methods of electron optics, and by 1933 Ruska made an instrument giving 12 000×, and commercial models were in use by 1938. However, G R Rüdenberg secured the first patent, which was upheld in a law suit in the USA (but not in Germany). Ruska’s work, supported by the Siemens and Halske company, was continued in a converted bakery in Berlin during the Second World War, until Soviet troops looted the laboratory. His transmission electron microscope eventually achieved up to 10 6 ×, compared with 2000× for an optical microscope. Ruska shared his Nobel Prize with G Binnig (1947– ) and of IBM, who from 1978 worked in Zürich on a complementary device, the scanning tunnelling microscope, using an ultrasharp tip at high voltage to explore conducting surfaces and valuable for the study of metal surfaces, giving resolution down to atomic size.

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