of the curves A + B + C and LL at any time is shown in the curve AA. The curve AA represents the activity at any time supplied by the change in radium A. The curve LL starting from the vertical axis is identical with the curve already considered, representing the decay of activity measured by the β rays for a long exposure (see Fig. 88).
| Time in minutes | Calculated value of activity | Observed value of activity |
|---|---|---|
| 0 | 100 | 100 |
| 10 | 96·8 | 97·0 |
| 20 | 89·4 | 89·2 |
| 30 | 78·6 | 80·8 |
| 40 | 69·2 | 71·2 |
| 50 | 59·9 | 60·8 |
| 60 | 49·2 | 50·1 |
| 80 | 34·2 | 34·8 |
| 100 | 22·7 | 23·2 |
| 120 | 14·9 | 15·2 |
This is shown by the agreement of the numbers in the above table. The first column in the table above gives the theoretical values of the activity deduced from the equation
for the values of λ2, λ3 previously employed. The second column gives the observed values of the activity deduced from the decay curve LL.
The close agreement of the curve LL with the theoretical curve deduced on the assumption that there are two changes, the first of which does not emit rays, shows that the change of radium B into C does not emit α rays. In a similar way, as in the curve I, Fig. 89, the curve LL may be analysed into its two components represented by the two curves CC and BB. The curve CC represents the activity supplied by the matter C present at the moment of