Contamination and irradiation, background radiation and doses in sieverts, and how to choose an isotope for a job in medicine or industry from its radiation and half-life.
What you will learn
- Tell contamination from irradiation and explain the precautions
- Compare doses in sieverts and millisieverts (Physics only)
- Name natural and man-made sources of background radiation (Edexcel all routes; AQA Physics only)
- Choose an isotope for a job from its radiation and half-life (Physics only)
- Explain how PET scanning works and why its isotopes are made nearby (Edexcel, Physics only)
Contamination and irradiation
Ionising radiation can damage cells and the DNA inside them, which can kill cells or lead to cancer.
- Irradiation: being exposed to radiation from a source outside you. Move away, or shield the source, and the exposure stops. An irradiated object does not become radioactive.
- Contamination: radioactive atoms get onto or into something (dust on skin, a gas breathed in, a tracer swallowed). The exposure goes on until the material is removed or decays.
Outside the body, alpha is the least dangerous (air and skin stop it). Inside the body, it is the most dangerous: it is next to living cells and is the most ionising. Precautions: tongs, gloves, distance, short times near the source, lead-lined storage.
Findings about the effects of radiation are published and checked by other scientists (peer review), so that safety rules rest on evidence that others have tested.
The rest of this lesson and its 13 practice questions are locked.
In this lesson
- Contamination and irradiation
- Background radiation and dose
- Choosing an isotope for a job (Physics only)
- PET scanning: Edexcel (Physics only)
13 practice questions, marked as you go; about 25 minutes in all.
Key terms
Natural, Man-made, Radiation dose, Sieverts, Which radiation, How long, Medical tracer, Sterilising, PET, Two gamma rays
In this unit: Atomic structure and radioactivity
The nuclear atom and how its model developed, isotopes, alpha, beta and gamma radiation, nuclear equations, half-life, the hazards and uses of radiation, and fission and fusion.
- Atoms, nuclei and isotopes
- Alpha, beta and gamma radiation
- Nuclear equations
- Half-life
- Hazards and uses of radiation
- Nuclear fission and fusion