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Bragg (Bragg), William Lawrence

( English physicist, Nobel Prize in Physics, 1915)

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Biography Bragg (Bragg), William Lawrence
March 31, 1890, Mr.. - July 1, 1971
English physicist William Lawrence Bragg was born in Adelaide (Australia), in the family U.G. Bragg, while Professor of Mathematics and Physics, University of Adelaide, and Gwendolyn (Todd) Bragg, daughter of Sir Charles Todd, South Australian Minister of Posts. B. first introduced to X-ray five years old, just a few weeks after their discovery by Wilhelm Roentgen. By studying these rays, senior Bragg has built a primitive X-ray machine, and just at this time a boy broke his arm. Uncle B. Young, a doctor by profession, took advantage of this apparatus to determine the nature of the fracture, which was first registered in Australia using X-rays in medicine.
Childhood B. held in Adelaide, but a year spent with his parents in France and England. He studied at the College of St.. Peter (secondary school in Adelaide) and in 1905. enrolled in the University of Adelaide, who graduated three years later with honors in mathematics. During training B. the university, his father continued the study of radioactivity and X-rays, and they often lead a lively discussion on the physical problems.
When father B: 1908 g. offered the post of professor of physics at the University of Leeds, his family moved to England.
On arrival at the beginning of next year. B. studied physics at Trinity College in Cambridge, Yves 1912. his exams with distinction in the natural sciences. Then he began research work under the guidance of J. J. Thomson at Cambridge and at the same time with his father, he studied X-ray diffraction patterns obtained earlier in the same year, Max von Laue. At the beginning of its work, Bragg, Sr. supported the idea, . that X-rays are streams of particles, . but he was impressed by the opening of the Laue, . discovered the, . that X-rays are diffracted (deflected) in crystals, . resulting in interference patterns, . similar to, . that gives light,
. Such pictures can only give a wave.
After discussing the diffraction of X-rays with his father, B. came to the conclusion that the wave interpretation of Laue's true, but that the description of the Laue diffraction unnecessarily complicated. Atoms in crystals are arranged in planes, and B. suggested that the diffraction pattern of a particular type is called a special arrangement of atoms in a specific variety of crystals. If so, then the X-ray diffraction can be used to determine the structure of crystals. In 1913, Mr.. He published equation, . later called the Bragg law, . describing angles, . under which should be directed beam of X-rays, . to determine the crystal structure of the diffraction pattern of X-rays, . reflected from the crystal planes,
. Then B. used his equation in the analysis of different crystals.
X-ray spectrometer, invented by his father in the same year, had a B. invaluable help, as the high sensitivity of the device allow to analyze the crystals are more complex than those that succumbed to the analysis of the previously known methods. The first substance that Bragg was studied using X-ray diffraction, was sodium chloride, or, more simply, salt. By 1913, Mr.. atomic theory of matter had already firmly established, and it was assumed that the chemical compounds are formed by molecules composed of atoms of different elements. For example, it was thought that sodium chloride is composed of molecules, each of which contains an atom of sodium and chlorine atom.
. Bragg Studies have shown that crystals of sodium chloride do not consist of molecules, and a certain way located sodium ions and chloride ions (ions - charged atoms)
. In the crystal molecules, no sodium chloride. Thus it was found the difference between molecular compounds (crystals which are composed of molecules) and ionic compounds (crystals which are composed of ions located in a certain way), . that was of great significance and has allowed scientists a much deeper understanding of the behavior of solutions,
. Working together, Bragg reduced to 1914. X-ray analysis of simple materials to the standard procedure. In the same year, B. was elected a member of the Academic Council and a lecturer at Trinity College.
The work done by B. and his father in 1912 ... 1914. laid the foundations of modern X-ray crystallography. Analysis of X-ray diffraction patterns is a powerful tool for mineralogists, metallurgists, ceramists and other researchers dealing with the atomic structure of materials. This method also enabled scientists to determine the structure of very complex molecules that gave rise to the whole area of molecular biology.
In 1915, Mr.. B. with his father was awarded the Nobel Prize 'for his services to study the structure of crystals using X-rays'. As was the First World War and the world was divided, the awarding ceremony was canceled. In an essay written in 1919, G.D. Granqvist from the Royal Swedish Academy of Sciences pointed out that thanks to the work of Bragg has not only to give a mathematical description of diffraction of X-rays, but also 'to approach the problem of crystal structure' experimentally. 'With the methods developed by Bragg - continued Granqvist, - opened a whole new world, which had been partially investigated by them with excellent care. "
In his Nobel lecture in Stockholm in 1922, B. summarized the work for which he was awarded. He finished the lecture by reasoning that 'there is an application of X-ray analysis of a deeper' than the definition of the structure of crystals, namely, 'investigation of the structure of the atom'. B. said: 'Since the wavelength of X-rays less than one atomic diameter', . if we use this term somewhat unclear, . and since the diffraction of these rays occurs mainly on the electrons of an atom, . We would be possible to get some idea of the distribution of these electrons in the same way, . how we make conclusions about the grouping of atoms'.,
. During World War II B
. served as technical adviser on sound zeroing (defining the location of enemy troops by the sound of artillery fire), going up the ladder to the rank of Major. After the war he returned to the post of lecturer at Trinity College. In 1919, Mr.. he succeeded Ernest Rutherford at the post of Professor of Physics, University of Manchester. Tam B. returned to his studies of crystal structure by X-ray. For many years he devoted to the study of complex structures arising in the silicate family of minerals, and this work has made a genuine revolution in mineralogy, putting it on a solid scientific basis. Subsequently, the results of research Used. proved very valuable for Linus K. Pauling.
Having completed the exploration of minerals by about 1930, B. took up the study of metals and metal alloys as party leader and practical work. In 1937, Mr.. he became director of the National Physical Laboratory, and the following year took the same time as professor of physics at Cambridge - a post which he retained until 1953, Mr.. At the end of World War II B. contributed to the establishment of the International Union of crystallographic and became its first president in 1949
In the late 30-ies. Max Perutz noticed B. crystallographic analysis of complex globular proteins. The Second World War interrupted these studies, however, after the war, they resumed. B. conducted studies and found financial support for this project and assembled a strong team of specialists to solve this problem. By that time, when B. left Cambridge, his team made significant progress in their studies. For two years, Perutz and John K. Kendrew made progress in the analysis of globular proteins, in particular hemoglobin. At the same time, Francis Crick, James D. Watson and Maurice Wilkins analyzed the structure of deoxyribonucleic acid (DNA). Support for the B. these studies, as well as tools and techniques developed under his guidance, have rendered an invaluable service here.
Over the lifetime of the B. Physics has changed so that, with the exception of early work, for which he received the Nobel Prize, all his research, in fact, have been away from the mainstream of physics. No less than his work in the field of experimental physics, he is known for the contribution he made to the chemistry, mineralogy, metallurgy and molecular biology. Although his great personal contribution to science, quite significant and the result of those groups that he organized and led. B. appreciated as an outstanding organizer of science, has enormous energy, tact and outlook.
Since 1954, Mr.. until his retirement in 1966. B. was director of the Royal Institution in London (post, which previously occupied by his father). All this time he worked on a lot of scientific education and often turned to the lay audience, especially to young children, telling them how exciting and beautiful may be the search for truth. The popular and talented orator, he was invited to read lectures on television. B. continued to give lectures, and after his retirement, as well as writing on scientific topics.
B. married Alice Hopkinson in 1921, they had two sons and two daughters. B. was amateur painter, and fond of literature and gardening.
In addition to the Nobel Prize, in the number of awards B. includes RцTblingen Medal of the American Mineralogical Society (1948), and the Hughes Medal (1931). Royal Medal (1946) and Copley Medal (1966) Royal Society. He received a knighthood in 1941. Member of the Royal Society, B. was also a member of Academies of Sciences of the United States, France, Sweden, China, the Netherlands and Belgium, as well as the French Society of Mineralogy and Crystallography.


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