A radioactive source is positioned close to a detector. The radiation reaching the detector from the source is recorded for 10 minutes while different materials are placed between the source and the detector. Which kinds of radiation does the source emit?
- A$\alpha$-particles and $\gamma$-rays
- B$\alpha$-particles only
- C$\beta$-particles and $\gamma$-rays
- D$\beta$-particles only