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Unformatted text preview: are independent of time. You can therefore use the amount of Pb 204 to estimate the amount of non-radiogenic Lead. in the Rubidium-Strontium decay the SR 87 is added to non-radiogenic Sr 87 , but we can get this latter from: (Sr 87 /Sr 86 ) non-radiogenic = 0.7 Similarly the Ar 40 in the Potassium-Argon decay will be added to the Ar 40 in the air, but, for the non-radiogenic component: (Ar 36 /Ar 40 ) air = 0.00337 We need also the fact that (K 40 /K total ) = 0.000119 Decay to a single daughter element When a simple one-to-one decay takes place we have daughter element D produced to the extent: D = P- P e-Lt = -P (e-Lt-1) where D=amount of daughter element, P of parent element and P is the original amount of the parent. L here is lambda, the decay rate. Of course by this definition L = ln2/T 1/2 . if P n (= P now) = P e-Lt then D = P n (e Lt-1) so t = (1/L)[/SUP> -1) so t = (1/L)[ln(1 + D/P n )]...
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- Fall '10