A radioactive isotope has a half-life of 40 minutes40\text{ minutes}40 minutes. The activity (number of emissions per second), AAA, of a sample of this isotope is measured at a certain time. What was the activity of the sample 80 minutes80\text{ minutes}80 minutes earlier?
A/4A/4A/4
A/2A/2A/2
2A2A2A
4A4A4A
144 exam-style questions on CIE IGCSE Physics 5.2.4a Half-life. Each one has a worked solution and a mark scheme showing where the marks go.