The setup illustrated is used to determine whether the flour in a cardboard packet is above a particular level. If the flour is higher than this level, it absorbs the radiation from the source, preventing it from reaching the detector. Which type of radiation is suitable for use?
- A$\alpha$-particles only
- B$\beta$-particles only
- Ceither $\alpha$-particles or $\beta$-particles
- D$\gamma$-rays only