Answer: Half the sample to decay.
- A All atoms to decay
- B Half the sample to decay
- C Sample to reach normal temperature
- D Radiation to decrease to zero
Correct answer: B. Half the sample to decay
Explanation: Half-life T(1/2): time for half the radioactive atoms in a sample to decay. After n half-lives: N = N<sub>0</sub>/2<sup>n.</sup>
Binding energy per nucleon rises sharply for light nuclei, peaks around iron-56 (the most stable nucleus), then slowly declines for heavier nuclei - which is exactly why fusing light nuclei or splitting heavy nuclei both release energy: each moves the products toward this stability peak.
Concept context
Radioactivity, nuclear reactions, fission, fusion, and binding energy.