Describe the properties of beta radiation that make it suitable for use in thickness monitoring of aluminium sheets in a factory.
Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).
A factory produces aluminium sheets of a fixed thickness. A beta source is used to monitor whether the sheet thickness remains constant during manufacture. The count rate detected on the other side of the sheet is used to check the thickness.
Model answer (4 marks)
Beta particles are fast‑moving electrons emitted from the nucleus.
Beta radiation has a medium penetrating power – it can pass through thin aluminium sheets but is attenuated by thicker sheets.
If the sheet becomes too thick, the count rate detected on the other side decreases; if the sheet becomes too thin, the count rate increases.
Alpha particles would be stopped by the aluminium sheet, and gamma rays would pass straight through and not be affected by small thickness changes, so beta is the most suitable for thickness monitoring.
Beta radiation has a medium penetrating power – it can pass through thin aluminium sheets but is attenuated by thicker sheets.
If the sheet becomes too thick, the count rate detected on the other side decreases; if the sheet becomes too thin, the count rate increases.
Alpha particles would be stopped by the aluminium sheet, and gamma rays would pass straight through and not be affected by small thickness changes, so beta is the most suitable for thickness monitoring.
Examiner tips
- Use the exact terms ‘beta particles’, ‘medium penetrating power’, ‘count rate decreases/increases’
- Explain why alpha and gamma are unsuitable
Common mistakes
- Confusing beta with alpha or gamma radiation
- Failing to mention the change in count rate with thickness
Mark scheme (4 marks)
- Beta particles are fast-moving electrons emitted from the nucleus
- Beta radiation has a medium penetrating power / can pass through thin aluminium sheets
- If the sheet becomes too thick, the count rate decreases / if the sheet becomes too thin, the count rate increases
- Alpha would be stopped by the aluminium sheet / gamma would pass straight through and not be affected by small thickness changes, so beta is the most suitable
Key terms in this question
Related
- All OCR GCSE Physics A: Gateway Science (J249) revision notes →
- How to answer a "Describe" question →
- Decode the mark scheme abbreviations →
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