On Atoms and Molecules

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    02-Jul-2016

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<ul><li><p>106 CURRENT TOPICS. [J. I;. I. </p><p>On Atoms and Molecules. ALBERT C. CREHORE. (Phil. Mug., May, Igzz.)-It must not be supposed that the regnant Rutherford atom alone is being considered. In this article you will find a photo- graph of models of the lighter elements and of their isotopes, wherein there is a far departure from the arrangement of a positively charged nucleus with its satellites of electrons. </p><p>G. F. S. </p><p>On the Molecular Scattering of Light in Water and the Color of the Sea. C. V. RAMAN. (Proc. Royal Sot., A To%)-The theory that the light of the sky owes its origin and colour to diffraction by the molecules of the atmosphere is now established on a firm experimental basis by the brilliant work of Cabannes and of Lord Rayleigh on the scattering of light by dust-free gases, and by the measurements of the transparency of the higher levels of the atmos- phere in the visual region of the spectrum, which have yielded results in close agreement with the calculated values. It is the purpose of the present paper to point out the part played by molecular diffraction in another of the great natural optical phenomena, that is, the colour exhibited by large masses of clear water when illumined by sunshine and viewed from above, the depth being so great as to provide a per- fectly black background for observation. </p><p>The theory of fluctuations, developed by Einstein and Smoluchowski, is applied to the problem and a formula is obtained in which the outstanding relation is this. When a beam of light is traversing a body of water the intensity of the light diffused perpen- dicularly to the direction of the ray is inversely proportional to the fourth power of the wave-length of the light. Volume for volume, water at 30 should scatter light 159 times as strongly as dust-free air under standard conditions. The result of the operation of the inverse fourth power law is that the shorter wave-lengths, the blue and violet, are diffused laterally to a much greater extent than the long reds and yellows. </p><p>The author combats Lord Rayleighs view that the blue of the sea is due to reflected skylight. Light reflected at the polarising angle from the surface of a liquid may be quenched by observation through a suitably oriented nicol. Hence by observing a tolerably smooth patch of water through a nicol at the polarising angle, the surface reflection may be got rid of. During a recent voyage, the writer made some observations by this method in the deeper waters of the hlediterranean ancl Red Seas, and found that the colour of the sea, so far from being extinguished when the sky-reflection is cut off is seen with wonderfully improved vividness and with saturated hues. </p><p>The entire trend of this paper is in opposition to the opinion that the color of large masses of water is due either to absorption or to reflection or to the presence of suspended matter. The scattering of the light is ascribed to the molecules of water. </p><p>G. F. S. </p></li></ul>