AQA · GCSE · Physics
Course version: 8463 · Version from Sept 2016
Students should be able to explain why the hazards associated with…
Full specification wording
Different half-lives of radioactive isotopes: Students should be able to explain why the hazards associated with radioactive material differ according to the half-life involved.
The half-life sets how the hazard is spread over time.
Checked against the AQA 8463 specification (opens in a new tab) on .
- Point 2 of 2
- 4 key terms
Study notes
From the checked teaching notes for this specification point.
The idea
The half-life sets how the hazard is spread over time. A short half-life gives a high activity, so a lot of radiation is emitted in a short period and the dose received in that time is large, but the source decays away quickly and soon becomes safe. A long half-life gives a much lower activity for the same number of nuclei, yet the material stays hazardous for thousands of years, which is why high-level waste from power stations is buried, stored in cooling ponds, sealed in metal containers, encased in concrete or transported in secure vessels. The same reasoning drives medical choices: a tracer uses a short half-life isotope so its activity falls quickly once the scan is done, limiting the patient's dose.
What earns the marks
- A short half-life meaning a high activity and so a large dose over a short time.
- A short half-life source quickly decaying away and becoming safe.
- A long half-life meaning a lower activity but a hazard lasting a very long time.
- A named precaution for long-lived waste, such as burying it, storing it in cooling ponds or metal containers, or covering it with concrete.
Common mistakes and how to put them right
Writing that a long half-life is more dangerous without saying why the hazard persists.
Claiming a short half-life source is harmless because it decays quickly.
Ignoring the type of radiation emitted, which also controls the hazard.
Saying waste is safe after one half-life, when only half of it has decayed.
Labelling waste as high, medium or low level instead of naming an actual precaution.
Exam tips
- Answer with both halves of the trade-off, activity now against duration later, because a one-sided answer caps the marks.
- For waste questions, give a physical precaution such as burial or concrete encasement; do not suggest simply storing it for one half-life, as it remains hazardous.
- Bring in the radiation type when a source is named, since alpha, beta and gamma need different handling.
Try the lesson
The start of the Different half-lives of radioactive isotopes: Students should be able to explain why the hazards associated with radioactive material differ according to the half-life involved. lesson, made from checked teaching notes for this specification point.
Have a go first
Why is a radioactive isotope with a very long half-life often considered hazardous for a long time?
Listen
The half-life sets how the hazard is spread over time. A short half-life gives a high activity, so a lot of radiation is emitted in a short period and the dose received in that time is large, but the source decays away quickly and soon becomes safe. A long half-life gives a much lower activity for the same number of nuclei, yet the material stays hazardous for thousands of years, which is why high-level waste from power stations is buried, stored in cooling ponds, sealed in metal containers, encased in concrete or transported in secure vessels. The same reasoning drives medical choices: a tracer uses a short half-life isotope so its activity falls quickly once the scan is done, limiting the patient's dose. A strong answer earns marks for these points. a short half-life meaning a high activity and so a large dose over a short time. a short half-life source quickly decaying away and becoming safe. a long half-life meaning a lower activity but a hazard lasting a very long time. a named precaution for long-lived waste, such as burying it, storing it in cooling ponds or metal containers, or covering it with concrete. Exam tip: Answer with both halves of the trade-off, activity now against duration later, because a one-sided answer caps the marks.
Key words
Say what each word means before you turn the card.
activity against duration
Try answering aloud or in your head before turning the card.
waste storage
Try answering aloud or in your head before turning the card.
medical tracers
Try answering aloud or in your head before turning the card.
hazard over time
Try answering aloud or in your head before turning the card.
See every definition
- activity against duration
- A short half-life gives a high activity and a large dose over a short time, while a long half-life gives a lower activity but a hazard lasting a very long time.
- waste storage
- High-level waste from power stations is buried, stored in cooling ponds, sealed in metal containers, encased in concrete or transported in secure vessels.
- medical tracers
- A tracer uses a short half-life isotope so its activity falls quickly once the scan is done, limiting the patient's dose.
- hazard over time
- The half-life sets how the hazard is spread over time, so a short half-life source soon becomes safe while a long half-life material stays hazardous for thousands of years.
There is more to this lesson
The full lesson goes on to check your understanding and help you earn the marks. Create a free account to carry on, with your progress saved.
A week of Premium from your first lesson · Then the free plan continues · No card, no charge
Test your understanding of Different half-lives of radioactive isotopes: Students should be able to explain why the hazards associated with radioactive material differ according to the half-life involved.
Active recall beats re-reading. Take an instant quiz now to test what you’ve learned and lock it into long-term memory.
A week of Premium from your first lesson · Then the free plan continues · No card, no charge