There are several isotopes of the element iodine.
Compare two different isotopes of iodine, such as Iodine-127 and Iodine-131.
A school laboratory technician wants to find the half-life of a radioactive isotope of iodine. They measure the count rate of a sample. Describe how they could correct the measured count rate for background radiation.
The technician measures the corrected count rate every 15 seconds. The table shows the results obtained:
Time (seconds)Corrected count rate (counts per second)0120159530764560604875389030105241201913515\begin{array}{|c|c|} \hline \text{Time (seconds)} & \text{Corrected count rate (counts per second)} \\ \hline 0 & 120 \\ \hline 15 & 95 \\ \hline 30 & 76 \\ \hline 45 & 60 \\ \hline 60 & 48 \\ \hline 75 & 38 \\ \hline 90 & 30 \\ \hline 105 & 24 \\ \hline 120 & 19 \\ \hline 135 & 15 \\ \hline \end{array}Time (seconds)0153045607590105120135Corrected count rate (counts per second)120957660483830241915Use the data in the table to estimate the half-life of this isotope. Explain your method clearly.