Monday, December 3, 2007

Sir Edward Victor Appleton (1892-1965)

Born in Bradford, he studied physics at Cambridge and spent World War 1 in the Royal engineers. Much concerned with persistent problem of the fading radio signal during the war, Appleton turned after the war to the study of the propagation of electromagnetic wave. It had been proposed by Oliver Heaviside and Arthur Kennelly in 1902 that some waves (known as sky waves) were reflected back to the earth by an electrical layer in the upper atmosphere. Appleton set out to confirm the suggestion experimentally and to explore the nature of the layer, which eventually became known as the ionosphere.

Suspecting that the fading was cause by interference, Appleton arranged for the BBC to vary the frequency of their transmitter while he recorded the strength the signal received some miles away in Cambridge. He found that a strengthening of the signal when the ground wave interfered constructively with the sky waves. Appleton calculated the height of the reflecting layer to be about 95 km and went on to show that it had been a complex structure. The top layer (F-region) of the ionosphere is often known as the Appleton layer.

From 1924 to 1936 Appleton was Wheatstone Professor of Experimental Physics at King’s College, London. After a spell as Jacksonian Professor of Natural Philosophy at Cambridge, he was appointed secretary to the department of Scientific and Industrial Research (1939-49). In 1944 he moved to Edinburgh University, where was vice chancellor until his death.

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