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Discovery and Development of X-rays
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2007-9-26
X-rays discovery was one of three discoveries of Physics (including X-rays 1896, radiation 1896 and electron 1897) in the late 19th century and the first 20th century, which symbolized the birth of modern Physics.
In the late 19th century, Cathode Ray was the subject of Physics study. Many labs carried out such researches. On Nov 8, 1984, German Physicist Roentgen put the cathode ray tube-CRT into a black paper bag, and switched off the lights in the lab. When he turned on the power of the discharge loop only to find a face plate coated with barium cyanoplatinite emitted fluorescence. If insert a thick book, a 2-3cm thick wood plate or several-centimeter thick hard rubber between the discharge tube and the face plate, fluorescence could still be seen. He again tested water, carbon dioxide or other liquid, and found they were "transparent" too to this ray, so were some metals made of copper, silver, gold, platinum and aluminium with the right thickness. Roentgen realized it was some special and never unobserved ray with an extremely strong penetrability. He stayed in the lab for days studying this ray. Six weeks later, Roentgen confirmed this new ray.
On Dec. 22, 1895, Roentgen and his wife photographed the first X-ray picture. On Dec. 28, 1895, Roentgen presented the first research communique The Preliminary Study of A New Ray to the Physical Institute of the University of Wurzburg, German, in which he called it X-ray as he wasn't sure of the nature of this new ray.
Since Roentgen¡¯s discovery of X-ray, many physicians were vigorously engaged in research and exploration. In 1905 and 1909 in succession, Barkla ever discovered the polarization phenomena of X-ray, but he was still uncertain what X-ray was, an electromagnetic wave or particle radiation? In 1912 German physician Laue discovered the diffraction phenomena of X-ray when penetrating the crystal, proving the undulatory property and the periodicity of internal structure of X-ray, and then released the paper titled Diffraction Phenomena of X-ray.
Before long after Laue published his article, father W. H. Bragg and son W. L. Bragg became concerned about it. W H. Bragg was the Physics Professor of University of Leeds and W L. Bragg just graduated from University of Cambridge and worked in Cavendish Lab. As supporters of X-ray particle formalism, they both tried to apply X-ray particle formalism to interpret Laue's pitures, but failed. After repeated studies, Junior Bragg succeeded in explaining Laue's experiment. He clearly elucidated the forming of X-ray crystal diffraction in a more concise pattern, and proposed the famous Bragg formula, nX=Zdsino, which not only proved Junior Bragg's interpretation true, but also validated obtaining crystal structure composition via X-ray. In November 1912, the 22-year-old Junior Bragg submitted his report of the research result titled Crystal¡¯s Role in Short-wave and Long Electromagnetic Wave Diffraction to the Cambridge Philosophical Society. In January 1913 senior Bragg devised the first X-ray spectrometer, to discover the Characteristic X-ray. After analyzing some crystal structures of alkali halide with Characteristic X-ray, Junior Bragg worked with his father and successfully determined the crystal structure of diamond, and validated it by applying Laue's method. The determination of diamond structure has perfectly illustrated the conclusion of the four bonds of carbon atom arraying in the form of the regular tetrahedron that chemists had long believed. As for the new emerging X-ray crystallography, it's helpful in analyzing the validity of crystal structure, and became recognized by physicists and chemists.
With more profound studies, X-ray has been extensively applied to crystal structure analysis and medical and industrial fields, which is of huge and far-reaching significance to the development of Physics and even the entire scientific technology in the 20th century.
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Organizer:
Beijing Municipal Association for Science & Technology
Undertaker: Beijing Science & Technology
Consulting Center,
Information Center of Beijing Municipal Association for
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