A scientist investigates how the activity of a radioactive isotope changes over time.
The table below shows the measured activity recorded by a detector.
Time / hoursMeasured activity / counts per second04201.52203.01204.5706.045 \begin{array}{|c|c|} \hline \text{Time / hours} & \text{Measured activity / counts per second} \\ \hline 0 & 420 \\ 1.5 & 220 \\ 3.0 & 120 \\ 4.5 & 70 \\ 6.0 & 45 \\ \hline \end{array} Time / hours01.53.04.56.0Measured activity / counts per second4202201207045The half-life of the isotope is known to be exactly 1.5 hours1.5\text{ hours}1.5 hours.
Why is each consecutive measured activity value after every 1.5 hours1.5\text{ hours}1.5 hours always greater than half of the preceding value?
Radioactive decay is a random process.
There is background radiation present in the laboratory.
The detector is positioned extremely close to the radioactive source.
The isotope undergoes multiple stages of decay.
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.