Radio-Activity

by Ernest Rutherford

224. Equations representing the activity curves. The equations representing the variation of activity with time are for convenience collected below, where λ₁ = 3·8 × 10^-3, λ₂ = 5·38 × 10^-4, λ₃ = 4·13 × 10^-4:—

(1) Short exposure: activity measured by β rays,

where I_T is the maximum value of the activity;

(2) Long exposure: activity measured by β rays,

where I₀ is the initial value;

(3) Any time of exposure T: activity measured by the β rays,

where