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Half-life · CSEC Physics

40 past-paper questions on Half-life, part of The Physics of the Atom, from every CSEC Physics paper on Quelpr.

Practise Half-life
  1. 3(b)(iii)2 marks· CSEC Physics · 1988 · Paper 2Calculate the half-life of a radioactive substance whose activity falls to 25% in 10 hours.
  2. 3(b)(iv)2 marks· CSEC Physics · 1988 · Paper 2The activity of a substance falls from 3 000 Bq to 750 Bq in 10 hours. What is its activity after a further fifteen hours?
  3. 3(c)3 marks· CSEC Physics · 1990 · Paper 2The activity of a sample of a radioactive element decreases to 1/4 of its original value in one hour. Calculate the half-life of the sample.
  4. 4(c)(i)5 marks· CSEC Physics · 1991 · Paper 2Plot a graph on the grid showing the decay of the 8.00 g mass over a period of 15 days.
  5. 4(c)(ii)1 mark· CSEC Physics · 1991 · Paper 2Using the graph or calculation, determine how much of the radioactive material remains after 5 days.
  6. 2(b)(i)4 marks· CSEC Physics · 1995 · Paper 2By reading off values of the count rate at suitable times, show that the half-life of Sample A is constant, and find its value.
  7. 2(b)(ii)1 mark· CSEC Physics · 1995 · Paper 2By considering the relevant graph, comment on the half-life of Sample B.
  8. 3(b)(i)2.5 marks· CSEC Physics · 1996 · Paper 2On Figure 5, draw the decay curve for 4 g of carbon-14. Label the graph clearly.
  9. 3(b)(ii)2.5 marks· CSEC Physics · 1996 · Paper 2On Figure 5, draw the decay curve for 4 g of carbon-15. Label the graph clearly.
  10. 4(c)(i)1 mark· CSEC Physics · 1998 · Paper 2Explain what is meant by the half-life of an isotope.
  11. 4(c)(iii)2 marks· CSEC Physics · 1998 · Paper 2Explain why a half-life of 8 days is suitable for medical uses compared to available isotopes with half-lives of 20 seconds and 2 years.
  12. 4(c)(iv)3 marks· CSEC Physics · 1998 · Paper 2Calculate after how many days 7/8 of a sample of 131_53 I will have decayed.
  13. 6(c)(i)2 marks· CSEC Physics · 2021 · Paper 2Define the term 'half-life'.
  14. 6(c)(ii)4 marks· CSEC Physics · 2021 · Paper 2At a certain time, a sample contains 8.0 × 10⁸ Radium nuclei. Calculate the number of α-particles emitted by the Radium nuclei in the next 4800 years.
  15. 6(c)(iii)1 mark· CSEC Physics · 2021 · Paper 2How much more time will elapse before the number of Radium nuclei remaining falls to 0.5 × 10⁸?
  16. 1(b)(i)2 marks· CSEC Physics · May/June 2022 · Paper 2Define the term 'half-life'.
  17. 1(b)(ii)5 marks· CSEC Physics · May/June 2022 · Paper 2From your graph, calculate the average half-life of the radioactive substance.
  18. 1(b)(iii)2 marks· CSEC Physics · May/June 2022 · Paper 2On your graph, use dotted lines to determine how long it would take for the activity of the sample to be reduced to ten disintegrations per minute from its original activity level. State the time taken.
  19. 1(b)12 marks· Physics Q1 1(b)Using your graph, calculate the average half-life of the sample, determined from the average of two or three values.
  20. 1(b)1 mark· Physics Q1 1(b)What is meant by the 'half-life' of a radioactive sample?
  21. 1(b)(i)5 marks· Physics Q1 1(b)(i)From your graph, determine the half-life of the sample.
  22. 1(b)(ii)6 marks· Physics Q1 1(b)(ii)Using your graph, determine a more accurate value of the half-life of the sample.
  23. 1(c)2 marks· Physics Q1 1(c)Use the graph to determine the activity of the sample after 25 days.
  24. 1(c)2 marks· Physics Q1 1(c)From your graph, and using dotted lines, determine how long it takes for the activity of the sample to be reduced to 10 disintegrations per second, from its original activity level.
  25. 1(d)(i)6 marks· Physics Q1 1(d)(i)From the graph, make TWO calculations of the half-life of the sample.
  26. 1(d)(ii)2 marks· Physics Q1 1(d)(ii)From your results in (d) (i), calculate the mean (average) half-life.
  27. 1(e)(i)6 marks· Physics Q1 1(e)(i)Estimate the count rate of the sample after 425 s
  28. 1(e)(ii)6 marks· Physics Q1 1(e)(ii)Estimate the count rate of the sample after 4 half-life periods.
  29. 2(b)(i)2 marks· Physics Q2 2(b)(i)Define the term 'half-life' of a radioactive substance.
  30. 2(b)(ii)4 marks· Physics Q2 2(b)(ii)The element thorium (Th) has a half-life of 24 days and undergoes beta-decay. Calculate the time it would take for 10 grams of thorium to decay to 1.25 grams.
  31. 3(d)2 marks· Physics Q3 3(d)How many half-lives would it take for a sample of Carbon-14 to be reduced to 1/32 of its original mass?
  32. 3(e)2 marks· Physics Q3 3(e)Given that Carbon-14 has a half-life of 5700 years, determine how long it would take for this reduction to occur.
  33. 5(d)5 marks· Physics Q5 5(d)One gram of a living plant containing Carbon-14, decays at about 16 disintegrations per minute. It is found that one gram of a dead plant decays at 1 disintegration per minute. The half-life of Carbon-14 is about 5500…
  34. 6(a)(i)2 marks· Physics Q6 6(a)(i)Define the term 'half-life'.
  35. 6(a)(ii)4 marks· Physics Q6 6(a)(ii)Calculate the half-life of Bismuth.
  36. 6(b)(i)2 marks· Physics Q6 6(b)(i)Define the term 'half-life'.
  37. 6(b)(i)4 marks· Physics Q6 6(b)(i)Calculate the probable age of the plant.
  38. 6(b)(ii)3 marks· Physics Q6 6(b)(ii)Calculate the half-life of lithium.
  39. 6(c)(i)4 marks· Physics Q6 6(c)(i)Use the data to determine: TWO different values of the half-life of the element
  40. 6(c)(ii)1 mark· Physics Q6 6(c)(ii)Use the data to determine: The average half-life of the element

Related topics in The Physics of the Atom