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Plaque commemorating J. J. Thomson's discovery of the electron outside the old Cavendish Laboratory in Cambridge Autochrome portrait by Georges Chevalier, 1923 Thomson c. 1920–1925 Thomson was elected a Fellow of the Royal Society (FRS) [ 24 ] [ 49 ] and appointed to the Cavendish Professorship of Experimental Physics at the Cavendish ...
1932 Antielectron (or positron), the first antiparticle, discovered by Carl D. Anderson [13] (proposed by Paul Dirac in 1927 and by Ettore Majorana in 1928) : 1937 Muon (or mu lepton) discovered by Seth Neddermeyer, Carl D. Anderson, J.C. Street, and E.C. Stevenson, using cloud chamber measurements of cosmic rays [14] (it was mistaken for the pion until 1947 [15])
In 1947, synchrotron radiation was discovered with a 70 MeV electron synchrotron at General Electric. This radiation was caused by the acceleration of electrons through a magnetic field as they moved near the speed of light. [72] With a beam energy of 1.5 GeV, the first high-energy particle collider was ADONE, which began operations in 1968. [73]
1897 J. J. Thomson discovered the electron; 1897 Emil Wiechert, Walter Kaufmann and J.J. Thomson discover the electron; 1898 Marie and Pierre Curie discovered the existence of the radioactive elements radium and polonium in their research of pitchblende; 1898 William Ramsay and Morris Travers discover neon, and negatively charged beta particles
Atoms were thought to be the smallest possible division of matter until 1899 when J. J. Thomson discovered the electron through his work on cathode rays. [37]: 86 [5]: 364 A Crookes tube is a sealed glass container in which two electrodes are separated by a vacuum.
Some particles including the positron were even discovered by using this device. By 1914, experiments by Ernest Rutherford, Henry Moseley, James Franck and Gustav Hertz had largely established the structure of an atom as a dense nucleus of positive charge surrounded by lower-mass electrons. [6]
Robert Oppenheimer argued strongly against the proton being the negative-energy electron solution to Dirac's equation. He asserted that if it were, the hydrogen atom would rapidly self-destruct. [8] Weyl in 1931 showed that the negative-energy electron must have the same mass as that of the positive-energy electron. [9]
In 1902, Philipp Lenard discovered that the maximum possible energy of an ejected electron is unrelated to its intensity. [12] This observation is at odds with classical electromagnetism, which predicts that the electron's energy should be proportional to the intensity of the incident radiation. [13]: 24 Albert Einstein c. 1905