Previous Page Historical Milestones in Physics - Page 4 Next Page


Year Description

1921
Total reflection, refraction, and diffraction of rays by ruled gratings discovered by Compton and Doan.

1922
A.H. Compton discovered the Compton effect.

1925
De Broglie suggested the possibility that each electron might be accompanied by a train of waves. Davisson and Germer discovered experimentally that sometimes the electron behaves not as a particle but as a wave (1927).

1925
H. Fricke and O. Glasser developed the thimble ionization chamber with air wall.

1926
High-voltage transformers with valve-tube rectification came into general use.

1928
O. Glasser, V.B. Seitz, U.V. Portmann, and J. Victoreen constructed the condensor dosimeter.

1930
C.C. Lauritsen developed the supervoltage single-section x-ray tube.

1930
Erection of memorial to Rontgen in Remscheid-Lennep (his birthplace) and beginning of Rontgen Museum.

1931
W.D. Coolidge built successful multisection cascading high-voltage tubes.

1931
Lawrence invented the cyclotron.

1932
Chadwick announced the discovery of the neutron.

1932
Heisenberg recognized that the nucleus of the atom consists of protons and neutrons.

1932
Cockroft and Walton disintegrated lithium with 700-kv protons and found that energy is released during the disintegration.

1932
D.H. Sloan constructed an r-f supervoltage x-ray generator.

1932
L.S. Taylor developed an American standard air ionization chamber to determine the value of the "roentgen".

1932
Urey discovered double-weight hydrogen, "heavy hydrogen" or deuterium.

1933
Anderson discovered the positron, the electrical opposite of the electron.

1933
Van de Graaff made great strides in improving the old-type electrostatic generator and obtained electric discharges of several million values. In 1948, mobile 2-million-volt units were commercially produced for radiography and therapy.

1934
Joliot and Irene Joliot-Curie discovered artificial radioactivity. They first produced radio nitrogen, then radio magnesium and radio silicon. Many hundreds of radioactive isotopes of elements are now known, many identified by x-ray spectra, including neptunium, plutonium, americinium, curium, berkelium, and californium.

1935
Fermi shot deuterons into uranium and other atoms and observed the phenomenon of artificial disintegration and fission, leading to atomic "piles" and bomb.

1937
The Fifth International Congress of Radiology accepted the international roentgen, first suggested in Stockholm, in 1928.

1937
Radiography and autoradiography by photoelectrons first mentioned by Seeman, later developed by Trillat and others.

1940
D.W. Kerst invented the betatron with which electrons were accelerated to 5 million volts by magnetic induction. Commercial 10- and 20-million-volt units have been developed, and in 1948 construction began on a 350-million-volt unit at the University of Illinois, completed in 1950.

1941
Very high intensity x-ray pulses of extremely short duration for flash radiography of rapidly moving objects made possible by Westinghouse Micronex surge generator.

1944
Two-million-volt x-ray tube commercially produced.

1945
Centennial of birth of Rontgen (March 27).

1945
Atomic bomb used in Japan.

1945
The synchrotron was invented as a means of electron acceleration to very high energies to compete with the betatron.

1946
Molecular structure of penicillin uniquely determined from x-ray crystal structure data, enabling synthesis of antibiotic, the best example of Fourier analysis of complex organic molecular structure now being carried out all over the world with the aid of electronic computers.

1946
New high-intensity tubes capable of delivering 5.5 million r/min make possible photochemical and biological studies, preparation of vaccines, and high-speed radiography heretofore impossible.

Previous Page Go To Top Next Page