Question

The radioactive decay of carbon-14 is first-order and the half-life is 5800 years. While a plant or animal is living, it has a constant proportion of carbon-14 (relative to carbon-12) in its composition. When the organism dies, the proportion of carbon-14 decreases as a result of radioactive decay and the age of the organism can be determined if the proportion of carbon14 in its remains is measured. If the proportion of carbon-14 in an ancient piece of wood is found to be one quarter that in living trees, how old is the sample?

Answer 1

If the half life is 5800 years, and there was only 1/4 of the Carbon 14 left in the wood remains, then 1/2 of the 1/2 life or 1/4 is 2900 years so the total age of the wood should be 5800  + 2900 = 8700 years old. We found some ancient highly compressed and water logged wood branches in an old glacial lake in the Highland Valley of BC., Canada and the lake deposits were up to 40,000 yrs old or just past the limit of Carbon 14 dating.