Carbon-14 has a half-life of 5730 yr. A living organism has an activity of 15.2 counts per minute (cpm)per gram of carbon. If a bone is determined to have an activity of 3.80 cpm per gram of carbon, how old is the bone?

Question

Quizplus · Accepted Answer

The activity of the bone is 3.80 cpm, which is 1/4th of the original activity (15.2 cpm). Since Carbon-14 has a half-life of 5730 years, it takes two half-lives for the activity to reduce to 1/4th of its original value. Therefore, the bone is 2 * 5730 = 11,460 years old, which is approximately 11,500 years.

Carbon-14 Has a Half-Life of 5730 Yr