How can a half-life be used to tell the age of a sample?
A)The half-life of an isotope is constant.
B)The amount of radioactive form depends on the amount of radiation in the surroundings.
C)The ratio between the radioactive form and the stable form depends on the archaeological record.
D)The ratio between the radioactive form and stable form varies regularly with time.
E)both C and D

Question

Quizplus · Accepted Answer

The half-life of a radioactive isotope is the amount of time it takes for half of the atoms in a sample to decay. As the decay process is regular and predictable, the ratio between the radioactive form and the stable form will vary regularly with time. Therefore, by measuring the ratio of radioactive isotope to stable isotope in a sample and comparing it to the known half-life of the isotope, scientists can determine the age of the sample.

How Can a Half-Life Be Used to Tell the Age