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2 marksRadioactivity

CAPE Physics Unit 2 · 2003 · Paper 2 · Question 9(c)(i)a)

Analysis of potassium and argon atoms in a moon rock sample shows the ratio of stable ^40 Ar atoms to radioactive ^40 K atoms is 10.3. Assume all argon atoms were produced by decay of potassium-40 with a half-life of 1.25 x 10^9 years.

Calculate the fraction of the original ^40 K atoms remaining in the rock.

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Other parts of this question

  1. 9(a)(i)Explain what is meant by the terms, 'activity', 'decay constant' and 'half life' of a radioactive substance.[3 marks]
  2. 9(a)(ii)State an equation relating the activity to the decay constant.[1 mark]
  3. 9(a)(iii)Draw a diagram to show the path of a stream of Beta particles and Gamma rays in a uniform electric field.[3 marks]
  4. 9(a)(iv)What instrument could be used to detect Beta and Gamma radiation?[1 mark]
  5. 9(b)(i)Write a nuclear equation to represent the ^99_42 Mo decaying to ^99_43 Tc.[2 marks]
  6. 9(b)(ii)A patient is injected with an 8.2 x 10^7 Bq sample of 99 Tc. How many gamma ray photons are initially produced within the patient each second?[2 marks]
  7. 9(b)(iii)A small tumor that has collected ^99 Tc emits 38 gamma ray photons per second at a given time. How many ^99 Tc nuclei are located in the tumor at this time?[2 marks]
  8. 9(c)(i)b)Calculate the number of half lives that has elapsed.[2 marks]
  9. 9(c)(i)c)Calculate the age of the rock.[1 mark]
  10. 9(c)(ii)From your answers in (c)(i) deduce the age of the solar system.[1 mark]

More practice: the rest of this paper · more Radioactivity questions · all CAPE Physics Unit 2 past papers