## Summary

Contrary to popular opinion, radiation is a natural phenomenon. It was discovered in 1896 by A.H. Becquerel who was studying the fluorescent properties of uranium salts.

We identify 3 distinct types of radioactive decay. Each type of decay liberates a large amount of energy:

1. Alpha radiation: the emission of a helium nucleus.
2. Beta (+ and -) radiation: the emission of either an electron (beta-) or a positron (beta+).
3. Gamma emission: the liberation of a high-energy photon.

Rollover each type of radioactive decay.

## Learning goals

• To distinguish the different types of radioactive decay.
• To specify that nearly all alpha decay or beta decay are accompanied by gamma emissions.
• To define the becquerel (Bq), a unit of measurement of activity in a radioactive sample (number of decays per second).
• To show that there are forms of ionizing radiation with very different penetrating properties. Gamma photons have strong penetrating properties which are used in nuclear medicine.