The ratio of number of atoms of 14C to 12C in living matter is measured to be 1.3×10−12 at the present time. A 12 g sample of carbon produces 180 decays/min due to the small amount of 14C in it. The half-life of 14C is nearly [1 year =3.15×107s]

[b] 14C12C=1.3×10−12 12 g contain 6.022×1023 atoms No. atoms of 14C=6.022×1023×1.3×10−12 =7.8286×1011⇒N=N0e−λt −dNdt=N0e−λt×λ⇒−dNdt=N×λ 18060=7.8286×1011×λ ⇒1λ=7.8286×10113⇒λ=0.3832×10−11 t1/2=0691λ=0.6920.3832×10−11=1.80×1011sec Half life =1.8032×1011sec=0.5740×104 year=5740 years.