Abstract
BY allowing a diverging pencil of Rontgen radiation to fall at nearly grazing incidence on one of the sets of cleavage planes of a crystal of rock-salt, and observing the intensity of the reflected pencil by a photographic plate, we find a series of well-marked and equal-spaced maxima in positions corresponding to equal increments of cos θ, where θ is the angle of incidence of radiation on the cleavage planes. In the directly transmitted beam there is no indication of variation of intensity with angle of incidence. We thus have what appears to be a series of X-ray spectra of different orders, due to agreement in phase of waves from successive layers of molecules. Calculating on this assumption we get a wave-length of the order of magnitude in agreement with that calculated from the velocity of ejection of electrons by a substance exposed to this particular radiation—that is, assuming the results of the experiments of A. L. Hughes and others on ultra-violet light are equally applicable to Röntgen radiation. While only few experiments have yet been made on which to base any interpretation, this is in agreement with what we have already observed. Of the experimental results there is no doubt, and we cannot at present suggest any probable explanation except the very obvious one of interference. Further experiments are in progress.
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BARKLA, C., MARTYN, G. An X-Ray Fringe System. Nature 90, 647 (1913). https://doi.org/10.1038/090647b0
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DOI: https://doi.org/10.1038/090647b0
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