The ratio of the abundance of carbon-14 to carbon-12 in a sample of dead wood is one quarter the ratio for living wood. If the half-life of carbon-14 is 5730 years, which one of the following expressions determines how many years ago the wood died?
A)2 × 5730
B)4 × 5730
C)0.75 × 5730
D)0.50 × 5730
E)0.25 × 5730

Question

Quizplus · Accepted Answer

The ratio of carbon-14 to carbon-12 being one quarter indicates that two half-lives have passed (since (1/2)^2 = 1/4). Therefore, the wood died 2 half-lives ago, which is 2 × 5730 years.

The Ratio of the Abundance of Carbon-14 to Carbon-12 in a Sample