Radium, its physics and therapeutics / [Dawson Turner].

  • Turner, Dawson (Dawson Fyers Duckworth)
Date:
1911
Catalogue details

Licence: Public Domain Mark

Credit: Radium, its physics and therapeutics / [Dawson Turner]. Source: Wellcome Collection.

    27/126 (page 9)
    RADIUM “) state of matter.” Radiant matter was prophetic, but he was ridiculed for these words. Since Crookes’ discovery our knowledge has ad- vanced; we now call these tiny particles electrons. The electron is a unit of negative electricity, a dis- embodied charge without material substance, and its apparent mass is only the one-thousandth of the mass of a hydrogen atom. Experiments by Sir J. J. Thomson and others have shown that the beta ray of radium is, to all intents and purposes, the cathode stream of the Crookes tube. Itis therefore no more a ray than the alpha ray ; it consists in a stream of electrons, identical in charge and mass with those found in a Crookes tube, but travelling more rapidly. The enormous electric force at the back of the electron in the Crookes tube is quite incompetent to give it the velocity with which it is ejected from radium. The velocity of the beta particle or electron is nearly equal to that of light; it is as high as 170,000 miles a second. Owing to their great speed and small size, they have much greater powers of penetration than the alpha particle. According to Rutherford, the relative penetrating power of the three types of rays is about in the ratio 1: 100:1,000. While a piece of mica or paper is sufficient to stop the alpha ray, it would take 1 centimetre of lead to insure that all the beta rays were intercepted. The beta rays, like the alpha, can be subdivided into different groups according to their range of penetration. Thus we can speak of hard