Half-lifeIB MYP Physics: Mind map

Exam questions on Half-life

1. A hospital in Singapore uses technetium-99m as a medical tracer. Its half-life is 6 hours. A sample is delivered at 08:00 with an activity of 400 MBq (megabecquerels).
   Calculate the activity of the sample at 14:00 on the following day.2 marks
2. A student measures the corrected count rate (background already subtracted) from a radioactive sample over 40 minutes. At 0 minutes the count rate is 160 counts per second. At 10 minutes it is 80 counts per second, at 20 minutes it is 40 counts per second, at 30 minutes it is 20 counts per second and at 40 minutes it is 10 counts per second.
   Describe the pattern shown by the count rate, using the data to support your answer.2 marks
3. A company is choosing a radioactive isotope for two jobs: as a medical tracer injected into a patient's blood, and as the radiation source in a smoke alarm. Isotope P has a half-life of 6 hours and emits gamma rays. Isotope R has a half-life of 432 years and emits alpha particles.
   Identify which isotope should be used as the medical tracer and explain your choice.3 marks