Compare the properties of alpha, beta and gamma radiation.

1. 1 · Open. Radioactive nuclei give out three kinds of radiation: alpha (α), beta (β) and gamma (γ).
2. 2 · Draw a comparison table.
   • Nature: helium nucleus / electron / electromagnetic wave.
   • Charge: +2e / −e / none.
   • Mass: about 4 times a hydrogen atom / very small / none.
   • Speed: up to about 1/10 c / up to about 9/10 c / c.
   • Ionising power: high / medium / low.
   • Penetrating power: low (paper) / medium (aluminium) / high (lead).
3. 3 · Draw the deflection diagram. [Diagram: source in a lead block between + and − plates; α bends towards −, β bends more towards +, γ goes straight]
4. 4 · Explain the opposite trend. The more a radiation ionises, the faster it loses energy, so the less it penetrates.
5. 5 · Common properties. All come from the nucleus, affect a photographic plate and cause fluorescence.
6. 6 · Real-life link. Gamma rays from cobalt-60 treat deep tumours; alpha sources are used in some smoke detectors.
7. 7 · Close. Thus α, β and γ differ in nature, charge and penetration, and gamma needs the strongest shielding.

Scoring tip: A neat four-column table (property, α, β, γ) with six rows earns most of the 7 marks.