Letter | Published:

Chemical and Electrical Changes induced by Light

Nature volume 74, page 564 (04 October 1906) | Download Citation

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Abstract

THE issue of NATURE for August 30 (p. 455) contains an abstract of a paper read before Section A of the British Association by Sir Wm. Ramsay and Dr. J. F. Spencer on the chemical and electrical changes induced by ultraviolet light, in which the “fatigue” shown by certain surfaces is discussed. I have for some time been engaged in an investigation of the fatigue shown by metals for the photoelectric effect, and have made a careful examination of the rate at which the photoelectric current decays in the case of a zinc plate, polished or amalgamated. A large Nernst lamp supplied with current from storage cells was used to give a steady source of light. The decay immediately after exposure to the light was very rapid, but after about twenty minutes became much slower. For a change taking place according to the “compound interest law,” as in the case of a monomolecular chemical reaction or a single purely surface effect; we know that the curve can be represented by an exponential term involving the time. In the case of zinc, I find that the activity at any instant can be represented with considerable accuracy by the sum of two exponential terms. It is possible to interpret this result somewhat on the lines followed by Rutherford in explaining the decay of the excited activity of radium or thorium, by supposing that a succession of changes takes place.

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  1. King's College, London, September 21.

    • H. S. ALLEN

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DOI

https://doi.org/10.1038/074564a0

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