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On a Simple Way of Obtaining the Half-Shade Field in Polarimeters
Published online by Cambridge University Press: 15 September 2014
Summary
The half-shade effect in polarimeters is usually obtained, either by the well-known, method of Laurent, or else by the more recent method of Lippich. In the former a quartz plate is employed to give the necessary rotation to one-half of the beam of polarised light propagated through the instrument; in the latter, a Nicol prism additional to the polariser serves the same end.
It occurred to the author that the required effect might be obtained very simply by merely interposing a glass plate in the beam of light, so that half the beam traversed it, in an oblique direction. It follows at once, from Fresnel's laws of the intensity of refracted light, that this will produce a slight rotation of the vibration-direction in the traversing half of the beam.
In practice the method is found to give very good results.
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- Copyright © Royal Society of Edinburgh 1906
References
page 522 note * For a description of the latter, see, for instance, Landolt's “Das optische Drehungsvermogen.”
page 522 note † The author afterwards learned that the same principle of rotation by selective reflection had already been applied to the polarimeter, although in a different manner, by Professor Poynting. See A Method of Making a Half-Shadow Field in a Polarimeter by two Inclined Glass Plates, by Poynting, J. H. So.D., F.R.S.,; B. A. Report, p. 662, 1899Google Scholar; also Catalogue of the Optical Convention, p. 224, 1905.
page 523 note * More exactly 42°·2.