XII. On the law of extraordinary refraction in Iceland spar
It is now some years since I carried out, in the case of Iceland spar, the method of examination of the law of refraction which I described in my report on Double Refraction, published in the Report of the British Association for the year 1862, p. 272. A prism, approximately right-angled isosceles,...
| Published in: | Proceedings of the Royal Society of London |
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| Format: | Article in Journal/Newspaper |
| Language: | English |
| Published: |
The Royal Society
1872
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| Subjects: | |
| Online Access: | http://dx.doi.org/10.1098/rspl.1871.0088 https://royalsocietypublishing.org/doi/pdf/10.1098/rspl.1871.0088 |
| Summary: | It is now some years since I carried out, in the case of Iceland spar, the method of examination of the law of refraction which I described in my report on Double Refraction, published in the Report of the British Association for the year 1862, p. 272. A prism, approximately right-angled isosceles, was cut in such a direction as to admit of scrutiny, across the acute angles, in directions of the wave-normal within the crystal comprising respectively inclinations of 90° and 45° to the axis. The directions of the cut faces were referred by reflection to the cleavage-planes, and thereby to the axis. The light observed was the bright D of a soda-flame. The result obtained was, that Huygens’s construction gives the true law of double refraction within the limits of errors of observation. The error, if any, could hardly exceed a unit in the fourth place of decimals of the index or reciprocal of the wave-velocity, the velocity in air being taken as unity. This result is sufficient absolutely to disprove the law resulting from the theory which makes double refraction depend on a difference of inertia in different directions. |
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