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Bohr,
Niels Henrik David Danish physicist Born: Copenhagen, Denmark, October 7, 1885 Died: Copenhagen, Denmark, November 18, 1962 | |||||||||
Avogadro Becquerel Bohr Doppler Einstein Geiger Heisenberg Hertz Kirchhoff Planck Roentgen Rutherford Schrodinger |
Bohr studied physics at the University of Copenhagen and received his doctorate there in 1911. He obtained a grant to study further and travelled to Cambridge where he worked under Rutherford. In 1916, he returned to the University of Copenhagen where he was appointed professor of physics. Bohr hit on the idea that if the theory that an atom consisted of a massive nucleus and a cloud of electrons, was combined with the quantum theory of Planck, it might be possible to explain how substances emitted and absorbed radiant energy. This was of vital importance in spectroscopy because it accounted for the spectral lines put to use by Kirchhoff. Radiation was emitted, Bohr claimed, when an electron changed its orbit and approached closer to the nucleus. When radiation was absorbed the electron was forced into an orbit farther from the nucleus. Bohr also pointed out that an electron could not take on just any orbit, being limited to certain fixed distances from the nucleus, thus generating or absorbing only whole quanta of energy. He called these orbital possibilities shells. In this way Bohr was able to account for the spectral lines of the hydrogen atom, although he worked only with circular orbits. The implications of elliptical and angled orbits were only considered at a later stage. This picture of the atom, viewing the electron as both a particle and as a wave, was the first reasonably successful attempt to explain nuclear structure, and Bohr was awarded the Nobel prize in physics in 1922, for his work. In 1939, Bohr visited the United States and at a scientific conference, announced the view that uranium underwent fission when bombarded with neutrons, causing a minor sensation among the scientists there. He also predicted, correctly, that the isotope uranium-235 was the isotope that would fission. Bohr returned to Denmark and was there when the German army invaded in 1940. After escaping to England, he returned to the United States where he worked on the atomic bomb project at Los Alamos. After the war, he returned to Copenhagen where he worked unremittingly on behalf of the development of peaceful uses of atomic energy. | |||||||||
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