Sir Edward Victor Appleton (September 6, 1892 – April 21, 1965) was an English physicist. After returning from active service in World War I, he became assistant demonstrator in experimental physics at the Cavendish Laboratory in 1920. He was professor of physics at the Univ. of London (1924–36) and professor of natural philosophy at Cambridge Univ. (1936–39). From 1939 to 1949 he was secretary of the Dept. of Scientific and Industrial Research. Knighted in 1941, he received the 1947 Nobel Prize in Physics for his contributions to the knowledge of the ionosphere, which led to the development of radar. September 6 is the 249th day of the year (250th in leap years). ... 1892 was a leap year starting on Friday (see link for calendar). ... April 21 is the 111th day of the year in the Gregorian calendar (112th in leap years). ... 1965 was a common year starting on Friday (the link is to a full 1965 calendar). ... Missing image Ypres, 1917, in the vicinity of the Battle of Passchendaele. ... 1920 is a leap year starting on Thursday (link will take you to calendar) Events January January 7 - Forces of Russian White admiral Kolchak surrender in Krasnoyarsk. ... 1939 was a common year starting on Sunday (link will take you to calendar). ... 1949 is a common year starting on Saturday. ... 1941 was a common year starting on Wednesday (link will take you to calendar). ... 1947 was a common year starting on Wednesday (link will take you to calendar). ... List of Nobel Prize laureates in Physics from 1901 to the present day. ... The ionosphere is the part of the atmosphere that is ionized by solar radiation. ... This long range radar antenna (approximately 40m (130ft) in diameter) rotates on a track to observe activities near the horizon. ...

For many years it had been postulated that there was a conducting layer in the upper reaches of the atmosphere. Marconi had been able to make his historic tranatlantic transmissions and to achieve this the signals had to be "bent if they were to reach their destination. In 1902 Oliver Heaviside and A E Kennelly independently proposed the idea of their being a conducting layer that reflected radio signals.

In his work, Appleton had observed that the strength of the radio signal from a transmitter a on a frequency such as the medium wave band and over a path of a hundred miles or so was constant during the day but that it varied during the night. This led to him to believe that it was possible that two radio signals were being received. One was traveling along the ground, and another was reflected by a layer in the upper atmosphere. The fading or variation in strength of the overall radio signal received resulted from the interference pattern of the two signals.

To prove his theory, Appleton used the British Broadcasting Corporation (BBC) radio broadcast transmitter at Bournemouth England. This transmitted a signal towards the upper reaches of the atmosphere. He received the radio signals near Cambridge, proving they were being reflected. By making a periodic change to the frequency of the broadcast radio signal he was able to measure the time taken for the signals to travel to the layers in the upper atmosphere and back. In this way he was able to calculate that the height of the reflecting layer was 60 miles above the ground.

External links

• Sir Edward Victor Appleton (http://www.nobel-winners.com/Physics/edward_appleton.html)
• Sir Edward Appleton (http://www.radio-electronics.com/info/radio_history/gtnames/appleton.php) A summary of the life and work of Sir Edward Appleton and his contribution to radio science.