AQA · GCSE · Physics
Course version: 8463 · Version from Sept 2016
Required knowledge of the properties of alpha particles, beta particles…
Full specification wording
Radioactive decay and nuclear radiation: Required knowledge of the properties of alpha particles, beta particles and gamma rays is limited to their penetration through materials, their range in air and ionising power.
Three properties, and they run in opposite directions.
Checked against the AQA 8463 specification (opens in a new tab) on .
- Point 5 of 6
- 4 key terms
Study notes
From the checked teaching notes for this specification point.
The idea
Three properties, and they run in opposite directions. Alpha is stopped by a sheet of paper or by skin, travels only a few centimetres in air, and is the most strongly ionising because its charge of +2 and slow speed let it interact with many atoms. Beta passes through paper but is stopped by a few millimetres of aluminium, travels about a metre in air, and is moderately ionising. Gamma is only reduced, never fully stopped, by thick lead or metres of concrete, travels very large distances in air, and is the least ionising. Range experiments use this: if the count-rate drops to background after about 3 cm of air, the source is emitting alpha only.
What earns the marks
- Alpha being stopped by paper or skin, with a range of only a few centimetres in air.
- Beta passing through paper but being stopped by a few millimetres of aluminium.
- Gamma requiring thick lead or concrete and having a very long range in air.
- The order of ionising power, alpha the most ionising and gamma the least.
- Using the fall of count-rate to background at a stated distance as evidence of the type emitted.
Common mistakes and how to put them right
Calling gamma the most dangerous in every situation, without saying whether the source is inside or outside the body.
Describing alpha radiation as harmless because it is stopped by skin.
Naming aluminium foil as the absorber without stating a thickness, which is ignored by the mark scheme.
Forgetting to subtract background radiation before deciding that a source has been completely absorbed.
Exam tips
- Learn the absorber, the range and the ionising power for all three radiations as a three by three table.
- When choosing an absorber to tell beta from gamma, say a sheet of aluminium of a stated thickness.
- Argue from the count-rate falling to background, not simply falling, when identifying a source.
Try the lesson
The start of the Radioactive decay and nuclear radiation: Required knowledge of the properties of alpha particles, beta particles and gamma rays is limited to their penetration through materials, their range in air and ionising power. lesson, made from checked teaching notes for this specification point.
Have a go first
Which type of nuclear radiation has the greatest ionising power?
Listen
Three properties, and they run in opposite directions. Alpha is stopped by a sheet of paper or by skin, travels only a few centimetres in air, and is the most strongly ionising because its charge of +2 and slow speed let it interact with many atoms. Beta passes through paper but is stopped by a few millimetres of aluminium, travels about a metre in air, and is moderately ionising. Gamma is only reduced, never fully stopped, by thick lead or metres of concrete, travels very large distances in air, and is the least ionising. Range experiments use this: if the count-rate drops to background after about 3 cm of air, the source is emitting alpha only. A strong answer earns marks for these points. alpha being stopped by paper or skin, with a range of only a few centimetres in air. beta passing through paper but being stopped by a few millimetres of aluminium. gamma requiring thick lead or concrete and having a very long range in air. the order of ionising power, alpha the most ionising and gamma the least. Exam tip: Learn the absorber, the range and the ionising power for all three radiations as a three by three table.
See it
Key words
Say what each word means before you turn the card.
penetration
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range in air
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ionising power
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identifying a source
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See every definition
- penetration
- The extent to which alpha particles, beta particles and gamma rays pass through materials, such as paper, skin, aluminium, lead or concrete.
- range in air
- The distance alpha particles, beta particles or gamma rays travel in air, from only a few centimetres to very large distances.
- ionising power
- How strongly alpha particles, beta particles or gamma rays ionise, with alpha the most ionising and gamma the least.
- identifying a source
- Using the fall of count-rate to background at a stated distance as evidence of the type of radiation emitted.
Label the diagram
Some boxes have lost their names. Pick the right name for each number.
1Box 1
2Box 2
3Box 3
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