3.8.1.2
Background radiation is always present and must be subtracted from measurements
Nuclear Structure & Radiation — AQA A-Level Physics
Key Definition
Background radiation — Ionising radiation present in the environment from natural and artificial sources.
Natural sources
- Radon gas from rocks and buildings — the largest contributor in the UK. Radon is an alpha emitter and dangerous if inhaled.
- Cosmic rays from space — protons from the Sun and supernovae collide with air molecules, producing gamma radiation.
- Carbon-14 in biological material — constantly replaced in living organisms, decays after death.
- Radioactive material in food and drink — e.g. potassium-40 in bananas (minuscule amounts).
Artificial sources
- Nuclear medicine — X-rays, CT scans, radioactive tracers, radiation therapy.
- Nuclear waste — small contribution, but dangerous for handlers.
- Nuclear fallout and accidents — e.g. Chernobyl. Extremely rare but catastrophic.
- To find the corrected count rate: subtract the background count rate from the measured count rate.
- AccuracyHow close a measurement is to the true or accepted value. High accuracy means low systematic error. is improved by repeating readings and taking readings over long time periods.