Three types of radiation: alpha, beta, gamma
Different particles or waves — different mass, charge and penetrating power.
An unstable nucleus emits one of three main types of radiation:
| Type | Symbol | Made of | Mass | Charge | Stopped by |
|---|---|---|---|---|---|
| Alpha | α | 2 protons + 2 neutrons (He nucleus) | 4 u | +2 | A sheet of paper / skin |
| Beta | β | Fast-moving electron from the nucleus | ~0 | −1 | A few mm of aluminium |
| Gamma | γ | High-energy EM wave (photon) | 0 | 0 | Thick lead / concrete (reduced, not stopped) |
Ionising power (how much the radiation damages atoms by knocking electrons off):
- α (highest — heavy, slow, double-charged → bumps into many atoms)
- β (medium)
- γ (lowest — but penetrates deeply, so still dangerous)
Penetration is the reverse order: γ penetrates most, α least.
- α = helium nucleus; β = electron from nucleus; γ = EM wave.
- Penetration: γ > β > α.
- Ionising: α > β > γ.
- Stopped by paper / aluminium / lead respectively.