Abstract
USING the apparatus previously described1, together with a set of Wratten Monochromat light filters Nos. 70–75, it has been possible to examine the variations of refractive index over a limited range of wave-lengths in the visible spectrum for several typical coals of varying rank. The Brewster angle was determined with each filter placed in turn before the light source, and the corresponding refractive index calculated. The determining factor limiting the accuracy of the measurements was the stability of the photo-cell amplifier. Under the most unfavourable conditions the limits of accuracy of the determination of refractive index were ±0·01. In general, the accuracy was greater than this.
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NATURE, 150, 690 (1942); and 151, 53 (1943).
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CANNON, C., GEORGE, W. Optical Dispersion for Coals. Nature 151, 225 (1943). https://doi.org/10.1038/151225a0
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DOI: https://doi.org/10.1038/151225a0
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