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Bragg, Sir William (Henry)

rays ray beam characteristic

(1862–1942) British physicist: discovered characteristic X-ray spectra; and developed (with his son) X-ray diffraction methods for determining crystal structures.
The Bragg method for studying the diffraction of X-rays by crystals. A narrow beam of X-rays from the X-ray tube (left) strikes the crystal; an ionization chamber is used to find the position of the diffracted beam.


Bragg is unusual among noteworthy researchers in that his first significant research was done when he was over 40. However, he had as co-worker after 1912 his son Lawrence and their success brought a Nobel Prize in 1915; they are the only father–son pair to share one. William studied at Cambridge and did so well in mathematics that he was appointed professor in Adelaide in 1886.

In 1904 he gave a major lecture on the new subject of radioactivity and was spurred by this to research on the subject. In 1909 he took up his duties as professor at Leeds and there began work on X-rays, inspired by recent work.

In 1913 Bragg found that, when X-rays are generated by the impact of high-energy electrons on a platinum target, the resulting continuous spectrum of X-rays contains some lines whose position is characteristic of the metal target was shortly to use these X-ray spectra in a valuable way. Bragg, with his son Lawrence, went on to examine the wavelengths of X-rays by using crystals (see entry above); their method founded X-ray crystallography.

W H Bragg moved to University College London in 1915, worked on submarine detection in the First World War, and became director of the Royal Institution in 1923.

Bragg, Sir (William) Lawrence [next] [back] Bradshaw, Tiny (Myron)

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