Question

A bone fragment has 67% of the parent Pb-210 remaining. The half-life of Pb-210 is 22 years. How old is the bone fragment?

0.03 years

21 years

12.7 years

15.1 years

Answer 1

The equation is
\[N _{t}/N _{0}=e ^{- \lambda t}\]
where, the constant of deintegration is
\[\lambda = \ln 2/t _{1/2}\]
and\[t _{1/2}\] is the half life of Pb-210
and
\[N _{t}/N _{0}\] is the quantity of Pb-210 remaining
The time is
\[t= 1/ \lambda *\ln(N _{0}/N _{t})\]