Present-day plant life has a carbon-14 decay rate of 16 disintegrations per minute (dpm) per gram of carbon. If a contemporary wooden chair were somehow preserved for the next 3,900 years, what ¹⁴C decay rate should be expected from the wood used to make the chair (t_1/2 = 5,730 yr)

Question

Quizplus · Accepted Answer

Carbon-14 has a half-life of 5,730 years, which means that after 5,730 years, half of the original amount of carbon-14 in a sample will have decayed. After another 5,730 years, half of the remaining carbon-14 will have decayed, and so on.

Therefore, if a wooden chair made from contemporary plant material were preserved for 3,900 years:

t = 3,900 years / 5,730 years per half-life = 0.681 half-lives

This means that only 32.5% of the original carbon-14 in the wood would remain. The remaining carbon-14 would decay at a rate of:

16 dpm / 2^(0.681) = 10 dpm

Therefore, the answer is D) 10 dpm.

Present-Day Plant Life Has a Carbon-14 Decay Rate of 16