Gamma radiation can be used in non-destructive industrial testing to inspect welds in steel pipes. Lead shielding is used to protect operators by absorbing the radiation.
Figure 1 shows how the percentage intensity of a gamma ray beam decreases as it passes through different thicknesses of lead shielding.
| Thickness of lead shielding (mm) | Percentage intensity (%) |
|---|---|
| 0 | 100 |
| 3 | 84 |
| 6 | 71 |
| 9 | 60 |
| 12 | 50 |
| 15 | 42 |
| 18 | 35 |
| 21 | 30 |
| 24 | 25 |
Use the data in Figure 1 to determine the thickness of lead shielding that will reduce the percentage intensity of the gamma ray beam by half.