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4 marksRadioactivity

CAPE Physics Unit 2 · 2002 · Paper 2 · Question 8(c)(i)

A radioactive mixture initially contains twice as many atoms of sodium-24 (t_(1/2) = 15 hours) as potassium-43 (t_(1/2) = 22 hours).

Calculate how long it will take for the number of atoms of each isotope to become equal.

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Other parts of this question

  1. 8(a)(i)In the radioactive decay law N = N0 e^(-λt), explain the meaning of EACH symbol.[2 marks]
  2. 8(a)(ii)Show that N = N0 e^(-λt) can be written as N = N0 2^(-t / t_(1/2)), where t_(1/2) is the half-life.[3 marks]
  3. 8(a)(iii)Explain what isotopes are.[1 mark]
  4. 8(a)(iv)Explain why carbon dating is unable to provide accurate age estimates for very old materials.[2 marks]
  5. 8(b)A nuclide 238_92 U decays to 214_82 X via FIVE successive decays, each emitting either an alpha particle or a beta particle. Determine the value of mass number…[6 marks]
  6. 8(c)(ii)Sketch the decay curves for the two isotopes on the same axes.[2 marks]

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