J. J. Thomson

Joseph John Thomson (often JJ Thomson, born December 18, 1856 in Cheetham Hill in Manchester, † August 30 1940 in Cambridge ) was a British physicist and Nobel laureate in physics. He discovered the electron in 1897.

Life

Joseph John Thomson was born in 1856, the son of Scottish parents near Manchester. His father was a bookseller. He attended from 1870, the Owen College in Manchester, which gave him a good scientific education. By the will of his parents he should become an engineer and study in a locomotive factory. But after the death of his father in 1873 were dashed these plans, since the funds were missing it. From 1876 he studied at Trinity College, University of Cambridge mathematics and physics, graduating with a Second Wrangler in the Tripos examinations in mathematics in 1880 (according to the bachelor's degree ). Also, the competition for the Smith Prize, which he received in 1880, he cut off in second. 1883 followed by the master's degree, at the same time he won the 1882 Adams Prize. In 1884 he received the prestigious Cavendish Professor of Physics at Cambridge who Lord Rayleigh held. On January 22, 1890 he married Rose Elizabeth Paget, one of the first researchers in the Cavendish Laboratory. They had two children, Joan Paget Thomson and George Paget Thomson, another Nobel Prize winner. Thomson himself was described as clumsy. He supervised the experiments and gave instructions. His assistants and students, but they tried to keep him from conducting the experiments. One of his students was Ernest Rutherford, who later received a Nobel Prize in Chemistry.

From 1918 until his death in 1940 he was Head of Trinity College and from 1916 to 1920 president of the Royal Society. He was buried in Westminster Abbey ( near Sir Isaac Newton ).

Work

Thomson (along with John Henry Poynting, George Francis FitzGerald, Oliver Heaviside and Joseph Larmor ) one of those, which further developed the electrodynamics of James Clerk Maxwell. In 1880 he initiated (but only approximately ) the Lorentz force from. In 1881 he investigated the behavior of moving charges and thereby introduced the concept of electromagnetic mass one, that is, it discovered that the electromagnetic energy behaves as if it increased the mass of a body. And 1893 was Thomson derive the associated with the electromagnetic energy pulse.

By examining the cathode ray Thomson succeeded in 1897, the experimental evidence for the George Johnstone Stoney in 1874 predicted the existence of the electron (the electron already in 1892 a fundamental role in the theories of Hendrik Antoon Lorentz and Joseph Larmor played ). Thomson was able to demonstrate that moving electrons were distracted by a magnetic field. This was disputed by Heinrich Hertz earlier. However, Thomson possessed now on better vacuum pumps, so that he could work in his cathode -ray tube with a significantly lower pressure.

This was the first discovery of a subatomic particle. Based on the developed Thomson Thomson's atomic model (also called " raisin cake " or " plum pudding model"), after which the very small electrons are embedded inside atoms like raisins in a cake. This model, however, was later disproved by Ernest Rutherford ( Rutherford's scattering experiment ) and replaced by the Rutherford atomic model cal a concentrated core of positive charge, surrounded by a shell of negative charges.

1906 Thomson was able to show that the envelope of the hydrogen atom contains exactly one electron. In 1913 he succeeded through the study of canal rays of neon evidence for the existence of different heavy atomic nuclei of an element ( in this case, 20Ne and 22Ne ). This, inter alia, Frederick Soddy introduced the theory of isotopes ago. Thomson is also known for his contribution to the development of the mass spectrometer.

Honors

1884 Thomson was elected as a member ( "Fellow" ) to the Royal Society, in 1894, the Royal Medal, 1902, the Hughes Medal, and in 1914 awarded him the Copley Medal. In 1906 he was awarded for his research on the electrical conductivity of gases, the Nobel Prize for Physics. Thomson was knighted in 1908 and included in the Order of Merit in 1912.

Writings (selection )

• Recollections and Reflections. G. Bell, London 1936 (online).