Radioactivity, Uses & DangersEdexcel IGCSE Physics: Flashcards
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What is background radiation?
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- What is background radiation?
- Ionising radiation present in the environment at all times, from natural (rocks, cosmic rays) and artificial (medical, industrial) sources.
- Name two natural sources of background radiation.
- Radioactive rocks/soil (e.g. granite, radon gas) and cosmic rays from space.
- What is the activity of a radioactive source, and its unit?
- The number of unstable nuclei decaying per second, measured in becquerels (Bq).
- Why does the activity of a radioactive source decrease over time?
- Because as nuclei decay, there are fewer undecayed nuclei remaining to decay further.
- Define half-life.
- The time taken for the activity (or number of undecayed nuclei) of a radioactive isotope to fall to half of its original value.
- A source has an activity of 400 Bq and a half-life of 2 hours. What is its activity after 6 hours?
- 3 half-lives have passed: 400 → 200 → 100 → 50 Bq.
- How is beta radiation used in industrial thickness gauges?
- The amount of beta radiation passing through a material (e.g. paper) varies with its thickness, allowing thickness to be monitored and controlled.
- How is radioactivity used to sterilise food or medical equipment?
- Gamma rays are used to kill bacteria and other microorganisms, extending shelf life or ensuring equipment is sterile.
- Define contamination.
- The presence of unwanted radioactive material on or in an object or person, causing continued exposure until it is removed.
- Define irradiation.
- Exposure of an object or person to radiation from an external source; exposure stops once away from the source.
- Name two dangers of ionising radiation to living organisms.
- It can cause mutations in DNA, and damage cells and tissue.
- How are the risks of radioactive waste disposal reduced?
- By storing waste securely (e.g. sealed in concrete or glass, buried deep underground) and monitoring it over the long term.