Microscopy: A Very Short Introduction by Terence Allen

Author:Terence Allen
Language: eng
Format: epub
ISBN: 9780198701262
Publisher: OUP Oxford
Published: 2015-02-14T05:00:00+00:00

Chapter 5

Electron microscopy and the dawn of atomic resolution

On Christmas day 1906, Ernst Ruska entered the world, the son of a professor in Heidelberg, a centre of German and international academic excellence both then and now. Ruska’s father had a large Zeiss microscope, a source of fascination for Ruska from a young age, as were the astronomical telescopes at the nearby observatory, run by his uncle. Ruska subsequently studied electrical engineering, and became a member of a team led by Max Knoll, helping to develop the cathode ray oscilloscope, in which a heated metal source generates a wide beam of electrons which are focused by two short electrically driven magnetic coils to form a small spot on a fluorescent screen. In the 1920s, Hans Busch had suggested that these magnetic coils were acting on the electron beam in the same way that glass lenses focus light beams. At the time, it was not known exactly how electrons behaved, as they were thought to be a stream of tiny particles, unlike the wave nature of light, but in 1924 Louis de Broglie, a French physicist, devised a theory suggesting that minute particles (electrons) could behave as waves, and consequently be diffracted. Ruska was aware of these findings, but as the wavelength of electrons was unknown at the time, he worried that there might be little or no advantage to using electrons for microscopy. Applying de Broglie’s equation, however, showed that the wavelength of electrons was ten times smaller than light (actually a thousand times smaller), meaning that electron microscopy should provide an improvement of one thousand times more than the resolution of light microscopy. Ruska went on to pioneer electron lens design, and in 1933 he built an electron microscope with a magnification of 12,000 times. Lacking the necessary funding to move his work to the next level, he moved from academia to the German electronics giant Siemens, and in 1939 the first commercially produced electron microscope was installed. Ruska often stood alone in the face of a sceptical scientific community with respect to electron microscopy, but was entirely justified, receiving the Nobel Prize for Physics in 1986 at the age of 80. In his acceptance speech he commented that ‘the doubt of others had the advantage of leaving the field uncrowded’. Ruska had survived long enough to enjoy his achievement, if only briefly, and died in 1988.

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