Societies and Academies

Abstract

LONDON Physical Society, June 1. G. F. HULL, S. E. GREEN and MARY BELL: The pressure of radiation. A historical statement. A brief account of some early experiments on radiation pressure, dealing in particular with the investigations of Lebedew and of Nichols and Hull. A. H. JAY: The estimation of small differences in X-ray wave-lengths by the powder method. It has been found possible by the use of a microphotometer to determine accurately the positions of lines at high angles of reflection on a powder photograph. With a powder photograph of clear colourless quartz taken with copper Ka radiation, the distance apart of the two component lines of a well-resolved doublet was measured to within 0-0002 cm. The measurements were then corrected for systematic errors-eccentricity of specimen, absorption of the radiation in the specimen, and divergence of the X-ray beam. The wave-length difference (Xa) was finally calculated in terms of the given wave-length V The value of (X-Xx) for copper Ka radiation is given as 3′833X. H. STAFFORD HATFIELD: The action of alternating and moving magnetic fields upon particles of magnetic substances. An explanation of the translatory movement observed by Mr. W. M. Mordey in magnetic particles subjected to a multi-phase alternating field. A. MOBBIS CASSIE: Time scale and electron relay used with a cathode ray oscillograph for the investigation of switch-gear and circuit phenomena. EGWYNNE-JONES: Note on the hyperfine structure in the arc spectrum of xenon. The hyperfine structures of the Xe I lines XX 9045, 9799 and 9923 are described and analysed, and the hyperfine separations of the terms 2p, and 2plfl are derived. It is also found that the lines 1st - 2p are readily self-reversed. Previous nuclear spin data are confirmed.