Question

The decay rate for a radioactive isotope is 9.29.2 percent per year. find the half-life of the isotope. round to the nearest tenth of a year.

Answer 1

Exponential decay is given by the equation

F = P(1 - r)^t

0.5 = 1(1 - 0.092)^t

0.5 = (0.908)^t

log 0.5 = log (0.908)^t

log 0.5 = t * log 0.908

t = (log 0.5)/(log 0.908)

t = 7.18

Answer: 7.2 years