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Later these particles were identified with the electron, discovered in cathode ray experiments by J. J. Thomson in 1897. This was connected with the theoretical prediction of the electromagnetic mass by J. J. Thomson in 1881, who showed that the electromagnetic energy contributes to the mass of a moving charged body. [2]
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]
This is a timeline of subatomic particle discoveries, including all particles thus far discovered which appear to be elementary (that is, indivisible) given the best available evidence. It also includes the discovery of composite particles and antiparticles that were of particular historical importance.
This became the classic means of measuring the charge-to-mass ratio of the electron. Later in 1899 he measured the charge of the electron to be of 6.8 × 10 −10 esu. [32] Thomson believed that the corpuscles emerged from the atoms of the trace gas inside his cathode-ray tubes. He thus concluded that atoms were divisible, and that the ...
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
Einstein, in 1905, when he wrote the Annus Mirabilis papers. 1900 – To explain black-body radiation (1862), Max Planck suggests that electromagnetic energy could only be emitted in quantized form, i.e. the energy could only be a multiple of an elementary unit E = hν, where h is the Planck constant and ν is the frequency of the radiation.
The electron was discovered between 1879 and 1897 in works of William Crookes, Arthur Schuster, J. J. Thomson, and other physicists; its charge was carefully measured by Robert Andrews Millikan and Harvey Fletcher in their oil drop experiment of 1909.
The Dirac sea is a theoretical model of the electron vacuum as an infinite sea of electrons with negative energy, now called positrons. It was first postulated by the British physicist Paul Dirac in 1930 [ 1 ] to explain the anomalous negative-energy quantum states predicted by the relativistically-correct Dirac equation for electrons . [ 2 ]