Half-Life Basics
IGCSE Edexcel Physics
7.11-7.13 Half-Life
Key Concepts:
Half-life is the time for activity or number of nuclei to halve.
Section A: Concept
1. Define half-life.
[2]
Section B: Calculations
2. A sample has 400 nuclei and half-life of 5 years. How many remain after 10 years?
[2]
3. A sample has activity 800 Bq and half-life of 2 hours. What is activity after 6 hours?
[2]
Total marks: 6
Mark Scheme
1.
Time for activity or number of nuclei to halve [2]
2.
Two half-lives: $400 \rightarrow 200 \rightarrow 100$ [2]
3.
Three half-lives: $800 \rightarrow 400 \rightarrow 200 \rightarrow 100\,Bq$ [2]