scispace - formally typeset
Search or ask a question

Showing papers by "S. Chandrasekhar published in 1954"


Journal ArticleDOI
01 May 1954
TL;DR: In this paper, the rotatory dispersion and the ultraviolet absorption spectrum of crystalline benzil have been studied and a rotatory power was measured from 9000 A to 3600 A in the ultraviolet right through the absorption band.
Abstract: The paper reports a study of the rotatory dispersion and the ultraviolet absorption spectrum of crystalline benzil. Transmission spectra have been photographed with varying thicknesses of the crystal. Even with the thinnest specimens (0.02 mm.) there is an almost complete cut off in the transmitted intensity beyond 3400 A marking the presence of an intense absorption band farther out in the ultraviolet. There is another comparatively feeble absorption which extends from 4500 A onwards into the shorter wavelength region of the spectrum with a maximum at, 3900 A. This band is markedly pleohroic. The rotatory dispersion has been measured from 9000 A in the infrared upto 3600 A in the ultraviolet right through the absorption band. A specimen of 0.03 mm. thick had to be used in order to penetrate the band. The crystal exhibits anomalous rotatory dispersion in the region of absorption. The one-term rotatory dispersion formula ρ2=6·27 λ2/λ2−(0·24)2]2 fits the data quite well except in the immediate vicinity of the absorption band. The temperature variation of the rotatory power has been measured for three wavelengths in the visible.

11 citations


Journal ArticleDOI
01 Jun 1954
TL;DR: In this article, the rotatory dispersion of quartz is accurately expressible from the visible to the extreme ultraviolet by a formula of the form\(rho = {{av^2 } \mathord{\left/ {\vphantom {{av ^2 } {\left( {v_0 ^2 - v^2 }, \right)^2
Abstract: The temperature variation of the rotatory power of quartz has been measured from 30° to 410° C. for a range of wavelengths extending from 6000 A to 2500 A. It is found that the temperature coefficient\(\left( {\frac{1}{{\rho _0 }} \frac{{\Delta \rho }}{{\Delta t}}} \right)\) exhibits an increase in the ultraviolet. The rotatory dispersion of quartz is accurately expressible from the visible to the extreme ultraviolet by a formula of the form\(\rho = {{av^2 } \mathord{\left/ {\vphantom {{av^2 } {\left( {v_0 ^2 - v^2 } \right)^2 }}} \right. \kern- ulldelimiterspace} {\left( {v_0 ^2 - v^2 } \right)^2 }}\), where\(v = \frac{1}{\lambda }\) Taking ‘a’ to be invariable with temperature (for which reasons have been put forward) but v0 to vary with it, the thermal variation of the rotatory power has been calculated over the whole range of wavelengths for the different temperatures. The theoretical calculation agrees very well with the observational data, the rate of shift of v0 being found to be roughly the same as that estimated from the thermal variation of the refraction. It is shown that theoretically we should expect the temperature coefficient to increase with decrease of wavelength, a fact which is confirmed by experiment.

6 citations