Compton, Arthur Holly 1892-1962

COMPTON, ARTHUR HOLLY 1892-1962

Particle physicist

Nobel Prize Winner

Arthur Holly Compton shared the 1927 Nobel Prize in physics for his discovery of the Compton effect, which lent strong support to Albert Einstein's important law of the photoelectric effect (1905).

Background

Born in Wooster, Ohio, Compton received a B.S. from the College of Wooster (1913) and an M.A. (1914) and a Ph.D. (1916) from Princeton University. After teaching at the University of Minnesota (1916-1917) and working on airplane-instrument design with the U.S. Army Signal Corps during World War I, Compton spent a year at Cambridge University, where he did research with Ernest Ruther-ford, the discoverer of the nucleus of the atom. He then accepted a post at Washington University in Saint Louis, where he taught physics from 1920 to 1923. He was at the University of Chicago from 1923 to 1945, after which he returned to Washington University, where he was chancellor (1945-1953) and Distinguished Service Professor of Natural Philosophy (1954-1961). During World War II he worked on the project to develop the atomic bomb.

The Compton Effect

In his research during the early 1920s Compton noticed that when an X ray or gamma ray strikes an electron, it bounces off at an angle to its original trajectory and loses energy in the process. Thisloss of energy is demonstrated by the fact that the X or gamma ray exhibits a longer wavelength, a characteristic of its drop in speed. As the gamma ray data was less conclusive than the data on X rays, when Compton published the results of his research in 1923, he limited his claims about this effect to X rays, but further research demonstrated that the Compton effect applied to gamma rays as well. Compton's discovery was a major break-through in determining that X rays and gamma rays were really particles, although people continue to call them rays. Physicists now speak of them as "wavy particles" because the subatomic particles do have wave like characteristics, such as frequency and wavelength.

Backing Up Einstein

Compton's work supported Einstein's employment of Max Planck's quantum theory (1900) to explain the photoelectric effect, whereby a light ray striking a metal plate "kicks out" electrons. Experiments showed that the frequency of the incoming light determined the number of electrons ejected. More electrons were dislodged from their atoms by blue light than by red light, which has a lower frequency than blue. Further, the speed of the ejected electrons varies according to the frequency of the light used. Thus, high-frequency ultraviolet light is the most efficient at producing the effect. By assuming that light rays are actually quanta (packets of energy) Einstein was able to devise equations to account mathematically for the photoelectric effect. Today light quanta are generally referred to as photons, a term coined by Compton in 1928.

Sources:

Niels H. de V. Heathcote, Nobel Prize Winners in Physics, 1901-1950 (New York: Schuman, 1953);

Marjorie Johnston, ed., The Cosmos of Arthur Holly Compton (New York: Knopf, 1967).