Charles Glover Barkla The Nobel Prize in Physics 1917

biography

Charles Barkla was one of the first scientists to help reveal the true nature of X-rays and, through later applications of his findings, the nature of the atom. He was born and educated in Liverpool, England, and received his bachelor's in physics from the University of Liverpool in 1898. From there he went to Trinity College, Cambridge, where he researched under Joseph J. Thomson, who had done significant work with cathode rays. Although Thomson would have tremendous influence on the direction of his work, Barkla remained at Cambridge solely for the chance to sing in its prestigious choir (he was a talented baritone and a popular soloist). In 1902 he transferred back to Liverpool, completing his doctoral studies in 1904.

During his college years, Barkla became interested in the phenomenon of X-rays, discovered by Wilhelm R?ntgen. At the time, scientists were uncertain about the nature of these rays: were they particles, like cathode rays, or transverse waves, like light rays? Thomson had developed a series of equations supporting the " ether pulse" theory proposed by George Gabriel Stokes (1819-1903). One of Barkla's first projects upon receiving his Ph.D.

was to test the ether pulse theory. It stated that X-rays should behave in a manner similar to the transverse electromagnetic waves in visible light. Barkla knew that visible light, when passed through certain substances, could be easily polarized; thus, if X-rays could also be polarized, they, too, must be transverse in nature. It took two years for him to assemble the proper equipment and obtain a clear result, at the end of which he succeeded in polarizing scattered X-rays. While striving to verify the ether-pulse theory, however, Barkla stumbled upon a much more important discovery. While using various samples of gases to scatter his X-rays, he noticed that different gases affected the intensity of the rays differently, and that the intensity of change was proportional to the gas's position on the periodic table of elements (and, thus, proportional to its atomic weight). Until this time, little was known about the properties of elements or the significance of their atomic numbers; Barkla 's findings became the cornerstone upon which a greater understanding of atomic structure was built. Barkla's later research also served as a starting point for Niels Bohr and Arnold Sommerfeld's quantum atomic model.

In 1917, Barkla was awarded the Nobel Prize for Physics for his discovery of the relationship between X-rays and atomic structure. Unfortunately, his later life was spent in almost total academic isolation. Always known as a great physicist but a weak theorist, Barkla began to ignore the groundbreaking work of other scientists. He rejected the quantum theory introduced by Albert Einstein and Max Planck, preferring to base his lectures strictly upon his own past research. In the end, he devoted his time to the pursuit of a mythical "J phenomenon" in radiation. Still, Barkla is recognized as a pioneer in X-ray experimentation.

Charles Glover Barkla was born on June 7, 1877 at Widnes, Lancashire, England, where his father, J.M. Barkla, was Secretary to the Atlas Chemical Company. He was educated at the Liverpool Institute and entered University College, Liverpool, in 1894 to study mathematics and physics, the latter under Oliver Lodge. He graduated with First Class Honours in Physics in 1898 and in the following year he obtained his master's degree. Also in 1899, he was awarded a research scholarship by the Royal Commissioners for the Exhibition of 1851 and he proceeded to Trinity College, Cambridge, to work in the Cavendish Laboratory with J. J. Thomson. He migrated to King's College during 1900 and in 1902 returned to Liverpool as Oliver Lodge Fellow. From 1905 to 1909 he was successively demonstrator, assistant lecturer in physics and special lecturer in advanced electricity at the University, and in 1909 he succeeded H. A. Wilson as Wheatstone Professor of Physics in the University of London. In 1913, Barkla accepted the Chair in Natural Philosophy in the University of Edinburgh and he held this position until his death.

Barkla's first researches concerned the velocity of electric waves along wires but in 1902 he commenced his investigations on R?ntgen radiation which were to occupy almost his whole life. His discovery of homogeneous radiations characteristic of the elements showed that these elements had their characteristic line spectra in X-ray and he was the first to show that secondary emission is of two kinds, one consisting of X-rays scattered unchanged, and the other a fluorescent radiation peculiar to the particular substance. He discovered the polarisation of X-rays, an experimental result of considerable importance for it meant that X-radiation could be regarded as similar to ordinary light. Barkla made valuable contributions to present knowledge on the absorption and photographic action of X-rays and his later work demonstrated the relation between the characteristic X-radiation and the corpuscular radiation accompanying it. He has also shown both the applicability and the limitation of the quantum theory in relation to R?ntgen radiation. The results of his findings are recorded in various papers which have appeared mainly in the Transactions and Proceedings of the Royal Society. He had a considerable reputation as an examiner in physics.

Barkla, a Fellow of the Royal Society, had several honorary degrees. He was appointed Bakerian Lecturer (Royal Society) in 1916 and he was awarded the Hughes Medal in the following year.

Charles Glover Barkla married Mary Esther, the eldest daughter of John T. Cowell of Douglas, Receiver-General of the Isle of Man, in 1907. They had two sons and one daughter. Their youngest son, Flight Lieutenant Michael Barkla, a brilliant scholar, was killed in action in 1943. Barkla's chief recreation was singing - he had a powerful baritone voice and he was a member of the King's College Chapel Choir, 1901-1902. Latterly, he had also become fond of golf. Barkla died at his home, Braidwood, Edinburgh, on October 23, 1944.

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