Published online by Cambridge University Press: 14 March 2018
Extinction is the increase in absorption that is to be expected when Bragg reflection of X-rays takes place in single crystals, and the corresponding decrease in intensity of reflection observed.
The increase of absorption was directly observed in 1914 in two ways. Using the ionization spectrometer, W. H. Bragg found that the amount of radiation transmitted by a crystal section was notably decreased when the transmitted beam had suffered reflection from a set of crystal planes.
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page 24 note 1 I am indebted to Dr. W. Ehrenberg of Birkbeck College, London, for this suggestion.