Radioactive decay and half-lifeEdexcel International A Level Physics: Mind map

Exam questions on Radioactive decay and half-life

1. A student sets up a Geiger–Müller tube and counter close to a long-lived source, whose half-life is many years, so its activity is effectively constant during the experiment. She records the number of counts in each of five successive 10 s intervals: 52, 47, 58, 44 and 55.
   Explain why the counts in the five intervals are different even though the activity of the source is constant.2 marks
2. Iodine-131 is a radioactive isotope with a half-life of 8.0 days. A hospital stores a sample of iodine-131 whose activity is 640 kBq. Use 1 day = 86 400 s.
   Calculate the number of undecayed iodine-131 nuclei in the sample when its activity is 640 kBq.2 marks
3. A student measures the corrected activity of a sample of a radioactive isotope at regular intervals and obtains the following values: 480 Bq at 0 s, 340 Bq at 40 s, 240 Bq at 80 s, 170 Bq at 120 s and 120 Bq at 160 s.
   Determine the half-life of the isotope from these results.3 marks