The Becquerel rays and the properties of radium / by Hon. R.J. Strutt.

  • Rayleigh Robert John Strutt Lord, 1875-
Date:
1904
Catalogue details

Licence: In copyright

Credit: The Becquerel rays and the properties of radium / by Hon. R.J. Strutt. Source: Wellcome Collection.

Provider: This material has been provided by the Royal College of Physicians of Edinburgh. The original may be consulted at the Royal College of Physicians of Edinburgh.

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    In this case the luminosity is spread over a large area. But by making the tube with a constriction in the middle (fig. 2), the glow is concentrated in the Fia. 2.—Pliicker's tube, for examining the spectra of rarefied, gases under electric discharge. The discharge passes between the platinum wires, a, b. These are sealed airtight into the elongated glass bulbs, c, d. The discharge is constricted, and increased in intensity by passing through the narrow tube e, which connects these bulbs. The gas is introduced at /, which can then be sealed off if desired. narrow portion, and its brightness greatly increased. Such tubes are very useful for examining the spec- trum of any desired gas under the electric discharge. They are known by the name of Pliicker, who was the first to use them. In the majority of gases the glow is most con- spicuous at a pressure of about of an atmosphere. Let us take the case of atmospheric air. In this case, at ^ 0f the atmospheric pressure, the negative electrode is seen to be surrounded by a blue glow, different in colour from the reddish colour along the length of the spark. The same thing can be seen in the spark at atmospheric pressure, though in this case the glow is almost confined to the surface of the negative electrode. At the low pressure it can be seen that the blue negative glow is separated by a small dark interval from the electrode itself (see fig. 1). Let the exhaustion now be carried further. It will be found that the blue negative glow spreads out and that the dark space becomes broader. A green luminosity begins to be visible on the wall of the tube opposite the negative electrode. At still lnghei exhaustions, such as can only be obtained by pio- longed use of the mercurial pump, it is found that a sharp patch of green fluorescent light is visible on