Higher Tier Only: Net Decline After Multiple Half-Lives
Part of Half-Life · GCSE GCSE Physics revision
This higher tier covers Higher Tier Only: Net Decline After Multiple Half-Lives within Half-Life for GCSE Physics. Revise Half-Life in Atomic Structure for GCSE Physics with 15 exam-style questions and 23 flashcards. This topic appears less often, but it can still be a useful differentiator on mixed-topic papers. It is section 10 of 13 in this topic. This section is most useful once the core foundation idea is secure, because it adds the detail that pushes answers higher.
Topic position
Section 10 of 13
Practice
15 questions
Recall
23 flashcards
🎓 Higher Tier Only: Net Decline After Multiple Half-Lives
You may be asked to calculate the number of half-lives that have passed, or to find the remaining activity after a given time.
Formula approach: Remaining activity = Initial activity × (½)ⁿ where n = number of half-lives
Example: A source starts at 3,200 Bq and has a half-life of 8 days. What is the activity after 40 days?
- Number of half-lives = 40 ÷ 8 = 5
- Remaining = 3,200 × (½)⁵ = 3,200 ÷ 32 = 100 Bq
You can also work backwards: if you know the current activity and the original activity, you can find how many half-lives have passed, and from that, the half-life itself (if you know the elapsed time).
Keep building this topic
Read this section alongside the surrounding pages in Half-Life. That gives you the full topic sequence instead of a single isolated revision point.
Practice Questions for Half-Life
What is the definition of half-life?
Explain what is meant by saying radioactive decay is 'random and spontaneous'.
Quick Recall Flashcards
15 questions on Half-Life — practise free
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