The Timeline

The Timeline

  • Submitted By: sidduart
  • Date Submitted: 11/25/2010 6:56 AM
  • Category: Science
  • Words: 682
  • Page: 3
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1885: Balmer discovers that the (visible) hydrogen spectrum’s wavelength can be expressed as:




, where n>2.

1895: X-rays are discovered by Rontgen. (Pg. 985) 1897: J.J Thomson establishes that Cathode Rays are actually fast moving beams of electrons (discovery of electrons); JJT finds specific charge (e/m) (Pg. 872); Becquerel discovers radioactivity. 1898: J.J Thomson establishes that when light falls on metal surface, electrons are emitted from that surface (Photoelectric Effect); the Curie couple discovers radium. 1899: Lenard and Millikan put forth Laws of Photoelectric Emission, which suggest that light exhibits characteristics of a particle, which goes against the Wave Theory, which was prevalent then. (Pg. 895) 1900: Planck puts forth his concept of light (and EM radiation, in general) being quantized and coming in packets called ‘photons’. (Pg. 896) 1901: Rontgen is awarded the Nobel Prize for his work on X-rays. 1903: The Curies are awarded the Nobel Prize for extracting radium. 1904: J.J. Thomson proposes his “plum-pudding” model of the atom (Pg. 939). 1905: Einstein explains the Photoelectric Effect on the basis of Planck’s quantum theory. (Pg. 896) .Einstein also proposes his idea of energy-mass equivalence: I$. 1906: Rutherford observes the scattering of α-particles. (Pg. 940) 1909: Geiger and Marsden make series of measurements on the deflection of the scattering of α-particles. (Pg. 940); Millikan establishes the value of ē (= 1.6 * 10^-19) and ascertains the quantization of charge through his oil-drop experiment.



1911: Rutherford comes up with an atomic model which provides an explanation for the scattering of α-particles (Pg.940 and Pg.942). However, a few drawbacks are present (Pg. 943). 1913: Bohr proposes his atomic theory for Hydrogen-like (i.e. with only one electron) atoms (ions) (Pg. 943). He makes use of Planck’s quantum theory; Max Moseley puts forth his law for...

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