Question

Carbon-14 has a half-life of 5,730 years. If the age of an object older than 50,000 years cannot be determined by radiocarbon dating, then A:carbon-14 levels in a sample are undetectable after approximately fourteen half-lives. B:carbon-14 levels in a sample are undetectable after approximately nine half-lives.C: the half-life of carbon-14 is too long to accurately date the object.D:a radioisotope with a shorter half-life should be used to date the object.

Answer 1

Radiocarbon dating is useful for determining ages of organic material from about 50,000 to 60,000 yrs. How many half-lives are needed to put you in this range?

Answer 2

Note that a longer half-life would leave more radioisotope to detect after a period of time while a shorter half-life would leave less.