Studies in Radioactivity (Paperback)

This historic book may have numerous typos and missing text. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1912 Excerpt: ...things being equal, is a measure of the value of kd for that substance, and therefore of the range in that substance of the ray of a certain definite initial speed. The experiment is conveniently carried out by making a thick lead ionisation chamber--the thick lead cuts out all but the penetrating rays--and inserting linings of different materials. The 7 rays must be kept at the same strength inside each lining, or if not, any differences must be allowed for. The following table shows results obtained in this way. The first column gives the material of the lining, and the second its thickness, which was enough to give the true value of kd except possibly in the cases of cardboard and aluminium. The third column gives the results obtained when the 7 rays had to pass through little more than the lead wall of the chamber, which was 0-47 cm. thick, and the fourth the results when the rays had also to pass through a lead screen 1-1 cm. thick. The figures are corrected for differences in volume and for differences in the strength of the 7 rays due to absorption in the The height of the chamber, which was cylindrical in form, was 15 cm. and the diameter 9 cm. The radium was placed on the axis of the cylinder, 10 cm. away from one end. The differences in the figures in the last two columns are reallv due to a change in the relative value for lead only. The rays have been so hardened by passing through the extra cm. of lead that the absorption coefficient (k) of the lead lining has fallen to the same value as that of the other metals. In the first case, there is a special production of softer /3 rays by the lead which does not take place in the second. The figures in the last column are relative measures of the range of the ft particle in the different substances op...