Chapter 25, Problem 98A

Interpretation Introduction

Interpretation: The question is to find how many half-lives 40,000 years represent.

Concept Introduction: The period of time it takes for one half of a radioactive isotope to decay is known as the half-life.

Answer to Problem 98A

40,000 years represent 7 half-lives of Carbon-14.

Explanation of Solution

Given information:

The half-life of Carbon-14 is 5730 years.

Dividing the number of years given by the half-life of Carbon-14,

  $\begin{array}{l}n=\frac{40000}{5730}\\ \approx 7\end{array}$

Conclusion

Hence, 40,000 years represent 7 half-lives of Carbon-14.