Topic 6 – Radioactivity: 6.12 Explain what is meant by background radiation

The idea

Background radiation is the low-level ionising radiation that is present all around us all the time, coming from natural and artificial sources rather than from a source you have deliberately set up. Natural sources include radioactive rocks and soil (such as granite), radon gas seeping from the ground, cosmic rays from space, and radioactive materials in food and drink. Artificial sources include medical uses such as X-rays and nuclear industry activities. An explanation should say that background radiation is always present, that it comes from a range of sources, and that it contributes a small dose to everyone. It is detected as a count rate even when no source is nearby.

What earns the marks

• Defines background radiation as low-level ionising radiation present in the environment at all times.
• Identifies natural sources such as rocks, radon gas, cosmic rays and food.
• Identifies artificial sources such as medical X-rays and nuclear industry.
• Explains that background radiation is detected even when no deliberate source is present.

Common mistakes and how to put them right

• Describes background radiation as radiation from a nearby radioactive source.

  Put it right by explaining it comes from the wider environment and is always present.

• Lists only one source and treats it as the whole explanation.

  Put it right by naming several natural and artificial sources.

• Claims background radiation is harmless in all cases.

  Put it right by explaining it contributes a small dose to everyone.

Exam tips

• Give a definition first, then support it with named sources to gain explanation credit.
• Separate natural from artificial sources so the answer is clearly structured.
• Mention that background radiation is detected as a count rate with no source present.