AQA A-Level Physics/Alpha, Beta and Gamma radiation

Exam note

For this topic, you to learn a lot of qualitative information, meaning that the questions in the exam will not only be testing your knowledge on how to do various calculations, but they will also ask you to explain and describe the underlying processes, so make sure you know it well.

Overall, you need to learn the three main types of radiation, what kind of material is sufficient to stop them, the risks and applications associated with radiation, the inverse square law for gamma radiation, and its investigation in required practical 12. See the official specification for more details.

Alpha (α) Radiation

• Nature- 2 protons + 2 neutrons, equivalent to a helium nucleus
• Range in air- Up to 100mm in air
• Deflection in a magnetic field- Easily deflected
• Absorption- Stopped by thin foil and paper
• Ionisation- Strongly ionising
• Energy of each particle- Constant for a given source

Beta (β) Radiation

• Nature- β- = electron; β+ = positron
• Range in air- Up to 1 metre
• Deflection in a magnetic field- Opposite direction to α particles, more deflection.
• Absorption- Stopped by approximately 5mm of aluminium
• Ionisation- Less ionising than α
• Energy of each particle- Varies up to a maximum

Gamma (γ) Radiation

• Nature- Photon of energy
• Range in air- Follows inverse square law
• Deflection in a magnetic field- Not deflected
• Absorption- Stopped by several centimetres of lead
• Ionisation- Very weakly ionising
• Energy of each particle- Constant for a given source