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Year Description

1897
Roentgen rays used in hospitals close to the front in the Greco-Turkish war, Tirah campaign, and Sudan and Boer wars, especially for locating bullets.

1897
Rutherford examined the radiations from uranium after Becquerel's discovery of radioactivity and found two types, which he alpha and beta rays. Later he found that alpha particles consist of nuclei of helium and that beta particles consist of the electrons discovered by Thomson.

1898
Marie and Pierre Curie announced the discovery of polonium in July and if radium in December.

1898
Villard discovered gamma rays and found them to be the same type of ray as the x-ray.

1899
A. Wehnelt suggested the use of electrolytic interrupters for induction coils.

1900
The Roentgen Society of the United States was found in St. Louis, Missouri.

1901
L. Benoist introduced an instrument to measure the penetration, or quality, of roentgen rays, called the penetrometer or radiochromometer.

1901
Dec. 10, Rontgen received the first Nobel prize in physics.

1902
G. Contremoulins introduced a fluoroscopic method to measure dosages in x-ray therapy.

1902
G. Holzknecht presented his first dosimeter for x-ray therapy, the chromoradiometer, consisting of a fused mixture of KCl and Na2CO3 which became discolored when exposed to roentgen rays.

1904
R. Sabouraud and H. Noire proposed a radiometer based upon the degree of discoloration of small pastilles of compressed barium platinocyanide under the effect of x-rays.

1905
R. Kienbock used strips of silver bromide photographic paper to estimate dosages in radiation therapy.

1906
Work on the perfection of cellulose acetate safety x-ray film was begun.

1907
Interrupterless transformers became available, using either the crossarm or the disk type of rectification.

1908
P. Villard proposed a dosage unit based upon ionization of air by x-rays.

1909
Millikan measured the charge of the negative electron in his "oil-drop" experiment.

1912
W. Friedrich, P. Knipping, and M. von Laue discovered that roentgen rays can be diffracted.

1912
C.T.R. Wilson studied fog tracks, produced by highspeed particles, with the cloud chamber developed in 1897.

1913
Th. Christen expressed radiation quality in "half-value layers."

1913
Coolidge built a successful roentgen tube with a hot-tungsten filamentary cathode and a solid tungsten anode.

1914
W.H. Bragg and W.L. Bragg discovered that roentgen rays can be reflected - The famous Bragg's law.

1914
H.J.G. Mosley related atomic number with wavelength characteristic of targets.

1914
W. Duane presented an "E" unit of roentgen-ray intensity.

1914
B. Szilard constructed a dosimeter to measure ionization and calibrated it in "mega-mega-ions."

1915
R. Furstenau measured x-rays dosages by determining the changes of resistance in a selenium cell under the influence of roentgen rays.

1916
W. Friedrich defined the "e" unit of dosage.

1916
Hull in the United States and Debye and Scherrer in Switzerland independently discovered the powder diffraction method.

1917
Self-rectifying x-ray generators were presented.

1919
Rutherford concluded that all matter is made up of protons (hydrogen), concentrated in a dense nucleus, around which the electrons revolve like planets.

1919
H.F. Waite constructed oil-immersed shockproof high-voltage generators with enclosed Coolidge tubes.

1920
Bohr accepted Rutherford's conception of the atom model assigned the electrons to orbits with certain levels of energy. The electrons can jump from orbit to orbit as they gain or lose energy. The Rutherford-Bohr atom model is based on the theory that the number of protons in the nucleus determines the number of electrons outside and therewith the place of the atom in the periodic table.

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