Chapter 21, Problem 37E

Interpretation Introduction

Interpretation: The Cobalt $-60$ is given to be a strong gamma emitter and has a half-life of $\text{5}\text{.26}\text{yr}$ . The replacement of cobalt $-60$ in a radiotherapy unit when its radioactivity falls to $75\%$ of the original sample is given. The time after which the Cobalt $-60$ needs to be replaced if an original sample was purchased in June $2016$ is to be calculated.

Concept introduction: The rate constant $\left(K\right)$ is calculated by the formula,

$K=\frac{0.693}{t_{1/2}}$

To determine: The time after which the Cobalt $-60$ needs to be replaced.