The Nobel Prize in Physics 1925
James Franck, Gustav Hertz
Born: 26 August 1882, Hamburg, Germany
Died: 21 May 1964, Goettingen, West Germany (now Germany)
Affiliation at the time of the award: Goettingen University, Goettingen, Germany
Prize motivation: "for their discovery of the laws governing the impact of an electron upon an atom"
Field: atomic physics
James Franck received his Nobel Prize one year later, in 1926.
Following Niels Bohr's theory for the structure of the atom, an experiment to verify it was made by James Franck and Gustav Hertz in 1913. A potential difference was applied to a tube containing a low pressure gas. When the potential difference was increased, the current through the tube also increased until it reached a certain voltage, then it was suddenly reduced. The result gave support for Bohr's theory in which the electrons have only specific discrete energies. The freely moving electrons, could at a certain energy, make the electrons of the gas atom to move to a new orbit.