. The London, Edinburgh and Dublin philosophical magazine and journal of science. too weak to produce anobservable effect. It is clear, therefore, that scattering may produce a risein the initial portion of absorption curves as well as a steepincline, or no observable effect, depending entirely on theexperimental arrangements. In order to obviate the effectof the scattering of the /3-particles on the initial portion ofthe absorption curve, the absorbing screens should be placeddirectly against the opening of the electroscope, in whichcase none of the scattered /3-particles will be lost. Appara
. The London, Edinburgh and Dublin philosophical magazine and journal of science. too weak to produce anobservable effect. It is clear, therefore, that scattering may produce a risein the initial portion of absorption curves as well as a steepincline, or no observable effect, depending entirely on theexperimental arrangements. In order to obviate the effectof the scattering of the /3-particles on the initial portion ofthe absorption curve, the absorbing screens should be placeddirectly against the opening of the electroscope, in whichcase none of the scattered /3-particles will be lost. Apparatus. In the ordinary cylindrical or rectangular shaped ionizationvessels, the /3-particles do not have equal paths, and conse-quently do not produce equal numbers of ions within thevessel. For this reason it was decided to use a hemisphericalionization vessel in the following investigation. A copperhemisphere, 30 cms. in diameter, was used for this purpose,and an appropriate electrode and electroscope were constructedas shown in fig. 2. The bottom of the ionization vessel was. removable. The active material was in all cases deposited asa thin layer on a thin aluminium foil (0*00025 cm.), and 854 Dr. A. F. Kovarik on the Absorption and this was in turn attached to a sheet of mica or aluminium o£a thickness slightly greater than would be necessary to stopall the a-rays which might be emitted by the active sheet was then placed inside the ionization vessel, activeside downward and over the central opening of the cover, towhich it was held by means of springs. The absorbing sheetswere also placed on the inside and were also held in positionby springs. The change of capacity produced by the slightelevation of a large number of absorbing sheets was found tobe negligible in the large vessel. The capacity of the instru-ment was about 10 units. Care was taken to obtainsaturation in all the experiments. With this arrangement the /3-particles have the radius ofthe vess
Size: 1602px × 1560px
Photo credit: © Reading Room 2020 / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1800, bookdecade1840, booksubjectscience, bookyear1840
