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Bragg (Bragg), William Henry

( English physicist, Nobel Prize in Physics, 1915)

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Biography Bragg (Bragg), William Henry
July 2, 1862, Mr.. - March 12, 1942
English physicist William Henry Bragg was born on a farm near Uigtona, Cumberland, the son of Robert John Bragg, a former officer in the merchant marine, and Mary (Wood) Bragg, daughter of the parish vicar Uestvordskogo. Mother B. died when he was 7 years old, and since then he lived with his uncle, who cared about his education. When he was 13 years old, his father sent him to King William's College, a secondary school on the Isle of Man, where the boy worked well in all subjects, except in church history and Greek.
In 1881, Mr.. B. enrolled at Trinity College in Cambridge, where he became a brilliant mathematics student. In the last year he attended lectures on physics Dzh.Dzh. Thomson, who reported B. vacancy at Adelaide University in Australia. B. applied for and was appointed professor of mathematics and physics, which had been held for 18 years. Since his training in physics gave way to his knowledge in mathematics, most of the long sea voyage, he spent studying textbooks on physics, which he took with him
B. arrived in Adelaide in 1885. Here he engaged in teaching activities, participated in the public life of the university, he worked in the Australian Association for the Advancement of Science. Almost 20 years he did not attempt to conduct any independent research. In 1889, Mr.. He married Gwendolyn Todts, daughter of Sir Charles Todd, South Australian Minister of Posts. They had two sons, the youngest of whom was killed in the First World War, and daughter. Over the years, B. occupied a prominent position in yuzhnoavstraliyskom society, but published only a few small articles.
In 1904, when B. was 42, he is deeply interested in the results of recent research in the field of radioactivity, including the work of Ernest Rutherford and Marie and Pierre Curie. He spent his first independent study in order to shed light on the phenomenon of radioactivity. Next three years B. studied the penetrating ability of alpha particles (nuclei of helium atom), which are emitted by atoms of radioactive substances in the decay, that is when their nuclei decay into other elements of the kernel. He found that the alpha particles emitted by these radioactive substance can be divided into well-defined groups, so that all the particles from one group to complete the same distance before they will be absorbed located in their path substance. The opening of these groups, which proved to be quite a surprise, showed that alpha particles are emitted only with certain initial velocities. This implies that the decay of the parent radioactive nucleus is held in stages, with each intermediate daughter nucleus emits an alpha particle with a different from other initial velocity. Consequently, traveled by an alpha-particle distance can be used to determine the type of nucleus, it emits a particle. This discovery, together with the pilot study of other radioactive radiations yielded B. international reputation.
In 1908, Mr.. B. was promoted to professor of physics at the University of Leeds and at the beginning of next year with his family returned to England. In the next few years, B. conducted extensive studies of the properties of X-ray and gamma-rays, assuming that they are more like a stream of particles than waves. During this period he led heated debate with Mr. Charles. Barkla about the nature of X-rays. However, in 1912. Max von Laue discovered the diffraction of (deviation) of X-rays on crystals, and showed error interference pattern reminiscent of a similar picture for the light. Since these pictures could be generated only by waves, B. stopped defending the corpuscular theory, saying that 'theory - is nothing more than a convenient and familiar tools'. The problem, he said, 'not to choose between two theories of X-rays, and to construct a theory which is compatible to the strengths of both points of view'. Quantum theory, created in the first quarter of XX century. works of Max Planck, Albert Einstein and Niels Bohr, led him to conclude that electromagnetic radiation (both light and X-rays) has the properties of both waves and particles.
Eldest son B., U.L. Bragg, who on his return to England, the family went to Cambridge to study physics, began in 1912. research under the guidance of J. J. Thomson. After discussing the problem of diffraction of X-rays with his father, U.L. Bragg came to the conclusion that the wave pattern of these rays, described Laue, true, but he felt that in his explanations too complicated details of Laue diffraction. U.L. Bragg has suggested that the atoms of a crystal are arranged in planes, and that X-rays reflected from these planes, forming diffraction patterns, which are determined by the specific arrangement of atoms. This theory implied that the diffraction patterns of X-rays can be used to determine the atomic structure of crystals. In 1913, Mr.. U.L. Bragg has published a formula that now bears the name of Bragg's law and indicating the angle at which to send X-rays on the crystal to determine its structure from the diffraction pattern.
. While his son worked on the theoretical aspects of X-ray diffraction, B
. invented a tool called X-ray spectrometer, designed for recording and measuring the wavelength of diffracted X-rays. Working together, using the Bragg X-ray spectrometer to determine the structure of various crystals, and by 1914, Mr.. they have reduced the analysis of simple crystals to the standard procedure.
. Through diffraction study of crystals of sodium chloride (salt), Bragg discovered that this substance does not consist of molecules, and located in a certain way of sodium ions and chloride ions (ion - a charged atom)
. Previously it was assumed that all compounds have a molecular nature that, for example, salt is formed by individual molecules composed of atoms of sodium and chlorine atoms. Opening Bragg that some compounds are ionic in nature and does not exist, for example, an object such as a molecule of sodium chloride, was of fundamental importance for chemists. Dutch chemist Peter Debye used these results in their studies of the fundamental behavior of ions in solutions.
FIELD B. X-ray spectrometer and his work with his son on the study of crystals formed the basis of modern science - the X-ray crystallography. X-ray diffraction technique used by experts in materials, minerals and ceramics and biologists. It has helped solve several problems, beginning with the diagnosis of internal stresses in metal parts of machinery and ending with the determination of the structure of biological molecules, such as deoxyribonucleic acid (DNA). Although modern X-ray spectrometers are highly automated, the concept and methods of analysis are the same that have been developed Bragg.
In 1915, Mr.. Bragg were awarded the Nobel Prize in Physics "for his merits in the study of crystal structure using X-rays'. A year before the outbreak of the First World War, and the awards ceremony was canceled. G.D. Granqvist from the Royal Swedish Academy of Sciences, in his essay, written in 1919, summarized the work of Bragg. Due to their methods, he said, 'opened a whole new world, which had been partially investigated by them with excellent care'. B. not read his Nobel lecture.
In the same year, when he received the Nobel Prize, B. became professor of physics at University College London. The First World War slowed down his research on the structure of crystals during the war, B. led the team responsible for the marine acoustics, and underwater acoustic sensors. After the war, he collected a large research team, which won the X-ray analysis of organic crystals, which led to the emergence of yet another modern science - molecular biology. Sam B. succeeded in determining the structure of naphthalene and its derivatives, while other members of the group studied different classes of organic compounds and conducted a theoretical analysis of X-ray diffraction of the complex crystals.
In 1923, Mr.. B. became director of the Royal Institution in London, and his team continued there study of organic crystals. A brilliant speaker, B. received many invitations from different parts of England to give a lecture for students and for their colleagues in the profession. During the Second World War B. actively worked in several government scientific advisory committees, so that the time for research has remained little. Nevertheless, he retained a keen interest in the work of the Royal Institution and continued to write articles about new developments in X-ray crystallography almost until his death, which occurred in London on March 12, 1942
. Known for its friendliness, generosity and simplicity, B
. revered traditions and craftsmanship. Being a deeply religious man, he was interested in the relationship between science and religion, and wrote a book about it. His greatest devotion was his family, and the death of his wife in 1929. was for him a terrible blow. B. was an avid golfer and a talented amateur painter, and in addition, played the flute.
In addition to the Nobel Prize, B. received many awards, including the Rumford Medal (1916) and Copley Medal (1930) Royal Society. He received a knighthood in 1920,. and the Order of Merit in 1931. President of the Royal Society from 1935 to 1940, B. was also a member of the leading scientific academies of other countries. He had 16 honorary doctorates British and foreign universities.


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