An industrial rolling mill uses an automated system to monitor and control the thickness of aluminium sheets (approximately 1.5 mm thick) as they are manufactured.
An engineer must choose a radioactive isotope for the source. The characteristics of four candidate isotopes are shown in the table below.
| Isotope | Half-life | Primary radiation emitted |
|---|---|---|
| A | 5.3 years5.3\text{ years}5.3 years | Gamma (γ\gammaγ) |
| B | 28 years28\text{ years}28 years | Beta (β−\beta^-β−) |
| C | 10 days10\text{ days}10 days | Beta (β−\beta^-β−) |
| D | 432 years432\text{ years}432 years | Alpha (α\alphaα) |
Which isotope is the most suitable for this application?
Isotope A
Isotope B
Isotope C
Isotope D