Abstract
LONDON Physical Society, Oct. 21.—F. Twyman: New apparatus for rapid spectrophotometry of liquids in the ultra-violet. A single exposure, usually of less than 20 sec., results in a set of spectra which embodies all that is necessary for plotting an absorption curve. J D. Stephenson: An experimental study of electrical discharge in gases at normal temperatures and pressures. By an investigation based on corona discharge it is shown that there is a fixed constant, the true breakdown strength of the gas, for all types of gas discharge at normal pressures.—G. A. Tomlinson: A new type of pendulum clock. A new method of taking accurately defined seconds signals from a pendulum is described, in which a photo-electric cell is used in conjunction with a special arrangement of multiple slits. This has been developed into a complete free-pendulum system, self-maintained in vacua by means of electrostatic impulses and having a closely governed arc.—S. E. Williams: A photographic method of deriving optical constants of the metals. A grating consisting of alternate strips of glass and metal of known dimensions gives diffraction spectra the relative intensities of which depend on the optical properties of the metal and glass. An expression has been found for the relative intensities of the central reflected image and the first principal diffracted image in terms of the reflection coefficients for the metal and glass and the phase change on reflection from the metal surface. By means of a photometric method which is described, the intensity ratio has been measured for two or more gratings of different proportions cut on the one mirror, enabling the deduction of the reflection coefficients and the change of phase. This is done both for light plane polarised in, and perpendicularly to, the plane of incidence, and the approximate Drude formulæ are used to calculate the optical constants. Simultaneous measurements can be made at several wave-lengths if the grating is illuminated with light from a source having a suitable line spectrum.
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Societies and Academies. Nature 130, 674–675 (1932). https://doi.org/10.1038/130674b0
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DOI: https://doi.org/10.1038/130674b0