Chapter 25, Problem 65A

Interpretation Introduction

Interpretation:

No. of atoms left after five half-lives are to be determined.

Concept introduction:

Half-life refers to the amount of time it takes for half of the radioactive isotope to decay.

Answer to Problem 65A

After $\text{5}$ half-lives, the sample is reduced to $\text{1/32}$ . No. of atoms left is 1 million.

Explanation of Solution

After the second half-life, the remaining half amount is further reduced into half, leaving $\text{1/4}$ of the amount of sample. After the third half-life, only $\text{1/8}$ of the sample will remain, then by the end of the fourth half-life, only $\text{1/16}$ of the sample remains. Finally, on the fifth half-life, only $\text{1/32}$ of the sample remains.