Pass Check: Radioactivity & Atomic Physics
Unstable nuclei emit radiation to become more stable, decaying at a fixed rate (half-life).
Radioactive decay
The random process where an unstable nucleus emits radiation to become more stable.
Half-life
The time taken for the number of radioactive nuclei in a sample (or its activity) to halve.
Alpha particle
A helium nucleus (2 protons, 2 neutrons) emitted from an unstable nucleus; weakly penetrating, stopped by paper.
Irradiation
Exposure of an object to radiation from a source, without the object becoming radioactive itself.
Quick check
Mixed quiz
1. State what happens to the mass number and atomic number during alpha decay.
2. State what an alpha particle consists of.
3. State one industrial use of radioactive sources.
4. State what a beta particle is.
5. State what background radiation is.
6. A radioactive isotope decays from 480 Bq to 60 Bq over 15 days. Calculate the number of half-lives that have passed.
7. Calculate the fraction of a radioactive sample remaining after 4 half-lives.
8. Using the answer above, calculate the half-life of the isotope in days.