. The London, Edinburgh and Dublin philosophical magazine and journal of science. diator produces a scattering of the primaryradiation, then the sorting out process will be simply adifference in degree for the two groups by different is no need to suppose there has been a change in typeof the primary radiation. Primary and Secondary y Bays. 929 II. Secondary y Rays.(1) The Distribution of Secondary y Radiation. Apparatus.—The electroscope was of lead 3 mm. thick and7 cm. cube. In the first experiments, it was supported on awooden arm which could be revolved so that the electros
. The London, Edinburgh and Dublin philosophical magazine and journal of science. diator produces a scattering of the primaryradiation, then the sorting out process will be simply adifference in degree for the two groups by different is no need to suppose there has been a change in typeof the primary radiation. Primary and Secondary y Bays. 929 II. Secondary y Rays.(1) The Distribution of Secondary y Radiation. Apparatus.—The electroscope was of lead 3 mm. thick and7 cm. cube. In the first experiments, it was supported on awooden arm which could be revolved so that the electroscopemoved round the arc of a circle of radius 25 cm. The centreof this circle was approximately the centre of the radium, about 300 mgrs.* of RaBr2, was contained in aplatinum vessel, and the electroscope was screened from thedirect radiation by a mass of lead. The arrangement wassimilar to that shown in fig. 1. The radiator consisted of ironplates lll cm. square. The electroscope was turned intothe different positions, and the readings taken with and 5 cms. //cms. | Tt//CK/V£SS Relation between amount of secondary radiation and thickness ofiron radiator. without the radiator, Seven positions of the electroscopeare taken; the first one measures the direct radiation and thelast one the secondary radiation at right angles to this. Theother positions are intermediate. In fig. 3 curves are plotted showing the effect of varying * This was kindly lent for the purpose by Professor Kutherford. It wassealed up in order to determine the rate of production of helium from it. 930 Mr. D. C. II. Florance on the thickness of radiator from 1*05 cm. to 11 cm. for eachposition of the electroscope round a quadrant of a circle. Eve has shown (Phil. Slag. Dec. 1^01) that for an increase;in thickness of radiator, the emergent secondary 7 radiationincreases rapidly till it reaches a maximum, and then itdecreases. The curve thus obta:ned can be expressed mathe-matically hv
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