Question

Upon examining layer M, you find that it contains a small proportion of the radioactive isotope - Potassium-40, which decays into Argon-40 with a half-life of 1.3 billion years. Assuming no contamination, what would be the age of a this layer if it contained 25% of Potassium-40 and 75% Argon-40?

Answer 1

t = 2.6 billion years

Step-by-step explanation:

If potassium becomes 25% of its initial value

so we can say it becomes half two times

as we know that 25% means it is 1/4 times of initial value

so we will have

`N = N_o e^(-\lambda t)`

here we know that

`N = 0.25 N_o`

`0.25 = e^(-\lmabda t)`

`ln 4 = ((ln 2)/(T_(1/2))) t`

`t = 2 T_(1/2)`

`t = 2(1.3 billion \: years)`

t = 2.6 billion years