Higher Tier Only: Net Decline After Multiple Half-Lives
Part of Half-Life — GCSE Physics
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 13 exam-style questions and 23 flashcards. This topic appears regularly enough that it should still be part of a steady revision cycle. 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
13 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).