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XXV.—Experiments on the Ordinary Refraction of Iceland Spar

Published online by Cambridge University Press:  17 January 2013

William Swan Esq.
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Extract

According to the theory devised by Huygens, to explain the phenomenon of double refraction in Iceland spar, a pencil of light transmitted through that substance is divided into two pencils; the index of refraction for the one being constant, while for the other it varies with the inclination of the transmitted light to the optical axis of the crystal.

Dr Wollaston, in 1802, verified the spheroidal form of the wave of light, which Huygens had assumed to account for the refraction of the extraordinary pencil, by a careful experimental investigation, conducted by means of his elegant instrument for “examining refractive and dispersive powers by prismatic reflection.” In 1810, Malus, in his Théorie de la Double Réfraction, also demonstrated experimentally the accuracy of the Huygenian law for the extraordinary pencil. I have not had an opportunity of consulting the memoir of Malus, so as to know the precise nature of his experiments, with reference to the refraction of the ordinary ray; but the object of Dr Wollaston's researches was simply to prove the law of extraordinary refraction, and the constancy of the index of refraction for the ordinary ray, is therefore tacitly assumed by him.

Type
Research Article
Information
Earth and Environmental Science Transactions of The Royal Society of Edinburgh , Volume 16 , Issue 3 , 1847 , pp. 375 - 378
Copyright
Copyright © Royal Society of Edinburgh 1847

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References

page 375 note * Philosophical Transactions, 1802, pp. 365 and 387.

page 375 note † See Experiment on the ordinary refraction of Iceland spar, by SirBrewster, David.—Notices and Abstracts of Communications of the British Association, 1843, p. 7.Google Scholar

page 376 note * Also in the Edinburgh New Philosophical Journal, January 1844.

note page 377* Silk is not the most suitable material for the purpose, owing to its transparency; but I could procure no better at the time.

page 377 note † I have also examined another prism, No. 1, and have found θ = 44° 23′ 2″, δ = 33° 11′ 0″, and μ=1·658362.

page 378 note * As the term, principal section, is employed in more than one sense, it may be proper to observe, in order to avoid ambiguity, that I use it to denote a plane perpendicular to both faces of the prism.— See Sir John Herschel's Treatise on Light, in the Encyclopædia Metropolitana, p. 370, art. 197.