Photograph of William Lawrence Bragg
William Lawrence Bragg
Detail map of Cambridge, England, United Kingdom Overview map of Cambridge, England, United Kingdom

A: Cambridge, England, United Kingdom

Discovery of the "Bragg Relation" in Crystallography

11/1912 to 2/1913
photograph of Lawrence Bragg in 1915
Lawrence Bragg in 1915

Five months after Max von Laue published his discovery of the defraction of x-rays in crystals, English physicist William Lawrence Bragg, at the age of 22, discovered that the regular pattern of dots produced on a photographic plate by an X-ray beam passing through a crystal could be regarded as a reflection of electromagnetic radiation from planes in a crystal that were especially densely studded with atoms. From this work the younger Bragg derived the “Bragg relation” or Bragg's law (nλ = 2d sin O). This relates the wavelength of the X-ray to the angle at which such a reflection could occur.

“The Diffraction of Short Electromagnetic Waves by a Crystal,” read 11 Nov. 1912 and published in Proceedings of the Cambridge Philosophical Society 17 (14 Feb. 1913) 43-57; W. H. Bragg, “X-rays and Crystals,” Nature 90 (23 Jan. 1913) 572.

Hook & Norman, The Haskell F. Norman Library of Science & Medicine (1991) No. 311.

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