Chapter 24, Problem 79A

Interpretation Introduction

Interpretation:

The distance at which the person have minimum exposure of $\text{0}{\text{.65mrem/ms}}^{\text{2}}$ needs to be determined.

Concept introduction:

Radiation is the emission of energy through space in the form of particles.

Answer to Problem 79A

The distance( ${\text{d}}_2$ ) at which the person have minimum exposure of $\text{0}{\text{.65mrem/ms}}^{\text{2}}$ is 0.67m.

Explanation of Solution

Given information,

$\begin{array}{l}{\text{I}}_1=\text{1}{\text{.15mrem/ms}}^{\text{2}}\\ {\text{d}}_{\text{1}}=\text{0}\text{.5m}\\ {\text{I}}_{\text{2}}=\text{0}{\text{.65mrem/ms}}^{\text{2}}\end{array}$

Relation between radiation intensity and distance is

$\begin{array}{l}{\text{I}}_{\text{1}}{\text{d}}_{\text{1}}{}^{\text{2}}={\text{I}}_{\text{2}}{\text{d}}_{\text{2}}{}^{\text{2}}\\ {\text{d}}_{\text{2}}{}^2=\frac{{\text{I}}_{\text{1}}{\text{d}}_{\text{1}}{}^{\text{2}}}{{\text{I}}_{\text{2}}}\\ {\text{d}}_{\text{2}}{}^2=\frac{1.15\times {(0.5)}^2}{0.65}\\ {\text{d}}_{\text{2}}{}^2=0.44\text{m}\\ {\text{d}}_{\text{2}}=\text{0}\text{.67m}\end{array}$

Conclusion

The intensity of radiation dependson the distance from the source. That is I is inversely proportional to d.