Since the ionization at any point above the plate is the resultant effect of the α particles coming from all points of the large radio-active layer, λ is not the same as the coefficient of absorption of the rays from a point source. It will however be proportional to it. For this reason λ is called the “absorption constant.”
Durack, _Phil. Mag._ July 1902, May 1903.
Bragg and Bragg and Kleeman, _Phil. Mag._ Dec. 1904.
Villard, _C. R._ 130, pp. 1010, 1178, 1900.
Rutherford, _Phys. Zeit._ 3, p. 517, 1902.
Paschen, _Phys. Zeit._ 5, No. 18, p. 563, 1904.
Paschen, _Annal. d. Physik_, 14, p. 114, 1904; 14, 2, p. 389, 1904. _Phys. Zeit._ 5, No. 18, p. 563, 1904.
Paschen, _Phys. Zeit._ 5, No. 18, p. 563, 1904.
Rutherford and Barnes, _Phil. Mag._ May 1905. _Nature_, p. 151, Dec. 15, 1904.
Becquerel, _C.R._ 132, pp. 371, 734, 1286. 1901.
Mme Curie, _Thèse présentée à la Faculté des Sciences_, Paris 1903, p. 85.
In a recent paper (_Phil. Mag._ Feb. 1905), McClelland has, in the main, confirmed the experimental results obtained by Eve. An electrometer was used instead of an electroscope. He finds, in addition, that the amount of secondary radiation depends on the angle of incidence of the primary rays, and is greatest for an angle of 45°. In a letter to _Nature_ (Feb. 23, p. 390, 1905), he states that more recent experiments have shown that the amount of secondary radiation from different substances is a function of their atomic weights rather than of their densities. In every case examined, the amount of secondary radiation increases with the atomic weight, but is not proportional to it.
Rutherford and McClung, _Phil. Trans._ A. p. 25, 1901.
Meyer and Schweidler, _Wien Ber._ 113, July, 1904.
Rutherford and Grier, _Phil. Mag._ Sept. 1902.
=115.= Besides their power of acting on a photographic plate, and of ionizing gases, the radiations from active bodies are able to produce marked chemical and physical actions in various substances. Most of these effects are due either to the α or β rays. The γ rays produce little effect in comparison. Since the β rays are similar in all respects to high velocity cathode rays, it is to be expected that they will produce effects similar in character to those produced by the cathode rays in a vacuum tube.