Physics 10 Dates 1881-1932
Professor: George Smoot
Approximate Dates of Some important Experiments and Theories, 1881-1932
1881 Michelson obtains null result for absolute velocity of earth
1884 Balmer finds empirical formula for spectral lines of hydrogen
1887 Hertz produces electromagnetic waves, verifying Maxwell's theory and accidentally discovering photoelectric effect
1887 Michelson repeats his experiment with Morley, again obtaining null result :
1895 Roentgen discovers x-rays
1896 Becquerel discovers nuclear radioactivity
1897 J. J. Thomson measures e/m for cathode rays, showing that electrons are fundamental constituents of atoms
1900 Planck explains blackbody radiation using energy quantization involving new constant h
1900 Lenard investigates photoelectric effect and finds energy of electrons independent of light intensity
1905 Einstein proposes special theory of relativity
1905 Einstein explains photoelectric effect by suggesting quantization of radiation
1907 Einstein applies energy quantization to explain temperature dependence of heat capacities of solids
1908 Rydberg and Ritz generalize Balmer's formula to fit spectra of many elements
1909 Millikan's oil drop experiment shows quantization of electric charge
1911 Rutherford proposes nuclear model of atom based on alpha particle scattering experiments of Geiger and Marsden
1912 Friedrich and Knipping and von Laue demonstrate diffraction of x-rays by crystals showing that x-rays are waves and that crystals are regular arrays
1913 Bohr proposes model of hydrogen atom
1914 Moseley analyzes x-ray spectra using Bohr model to explain periodic table in terms of atomic number
1914 Franck and Hertz demonstrate atomic energy quantization
1915 Duane and Hunt show that the short wavelength limit of x-rays is determined from quantum theory
1916 Wilson and Sommerfeld propose rules for quantization of periodic systems
1916 Millikan verifies Einstein's photoelectric equation
1923 Compton explains x-ray scattering by electrons as collision of photon and electron and verified experimentally
1924 De Broglie proposes electron are waves of wavelength h/p
1925 Schrodinger develops mathematics of electron wave mechanics
1925 Heisenberg invents matrix mechanics
1925 Pauli states exclusion principle
1927 Heisenberg formulates uncertainty principle
1927 Davisson and Germer observe electron wave diffraction by single crystal
1927 G. P. Thomson observes electron wave diffraction in metal foil
1928 Gamow and Condon and Gurney apply quantum mechanics to explain alpha decay lifetimes
1928 Dirac develops relativistic quantum mechanics and predicts existence of positron
1932 Chadwick discovers neutron
1932 Anderson discovers positron