Radioactivity
Year 11 (IGCSE) 🌡️ Energy & Thermodynamics Describe alpha, beta and gamma radiation; understand half-life.
☢️ Types of Radiation
Unstable nuclei emit radiation to become more stable. Three main types:
| Type | Symbol | Charge | Mass | Stopped by |
|---|---|---|---|---|
| Alpha (α) | ⁴₂He | +2 | 4 u | Paper, skin |
| Beta (β) | e⁻ | -1 | ≈0 | 3 mm aluminium |
| Gamma (γ) | γ | 0 | 0 | Several cm lead |
⏱️ Half-Life
The half-life is the time for the number of radioactive nuclei (or activity) to halve.
Half-Life
$$N = N_0 \times \left(\frac{1}{2}\right)^n \quad \text{where } n = \frac{t}{t_{1/2}}$$Example: Start with 800 Bq, half-life = 2 h.
After 6 h (3 half-lives): 800 → 400 → 200 → 100 Bq
After 6 h (3 half-lives): 800 → 400 → 200 → 100 Bq
🛡️ Uses & Hazards
Radiation has many uses (medical imaging, cancer treatment, carbon dating) but must be handled safely.
Ionising radiation can damage DNA and cause cancer. Always use lead shielding, increase distance, and reduce exposure time.
Ready to test yourself? Click the Quiz tab above to answer questions on this topic!
☢️ Radioactive Decay Calculator