Paper 3 Nuclear Physics Drills

Q1 Exponential Decay

A radioactive sample has initial activity $8.0\times 10^4\mathrm{Bq}$ and half-life $12\mathrm{h}$.

1. Calculate the activity after $36\mathrm{h}$. [2]
2. Calculate the decay constant in ${\mathrm{s}}^{-1}$. [3]
3. Explain why the sample is not completely inactive after many half-lives. [2]

Q2 Fission and Fusion Energy

1. Explain why both fission of heavy nuclei and fusion of light nuclei can release energy. [4]
2. A fission reaction has mass decrease $0.190\mathrm{u}$. Calculate energy released in MeV, using $1\mathrm{u}=931.5\mathrm{MeV}/c^2$. [2]
3. Explain why fission can lead to a chain reaction. [2]

Q3 Radiation Safety

1. Compare alpha, beta and gamma radiation in ionising power and penetration. [4]
2. Distinguish irradiation from contamination. [2]
3. State two ways to reduce dose from an external gamma source. [2]