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4 marksRadioactivity

CAPE Physics Unit 2 · May/June 2025 · Paper 2 · Question 3(b)(iv)

Technetium-99m is a radioactive tracer widely used in diagnostic medical imaging. A sample of the tracer with an initial activity A₀ of 600 Bq is injected into a patient. The activity, A, is measured at time, t, in two-hour intervals. The results obtained are recorded in Table 2.

Use your results from (b)(iii) to calculate the time, t, required for the activity in the patient's body to decrease to one per cent of its value at the time of injection.

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Other parts of this question

  1. 3(a)(i)Use an annotated diagram to describe the Geiger-Marsden α-particle scattering experiment.[6 marks]
  2. 3(a)(ii)Using the results from this experiment, state the TWO major conclusions regarding the nuclear model of the atom.[2 marks]
  3. 3(b)(i)Complete Column 3 and Column 4 of Table 2.[2 marks]
  4. 3(b)(ii)On the grid provided in Figure 5 on page 17, plot a graph of ln (A/A₀) versus time, t. Draw the line of best fit through the points.[4 marks]
  5. 3(b)(iii)Determine the gradient of the graph in (b)(ii) and use it to find the half-life of Technetium-99m.[5 marks]
  6. 3(b)(v)Express the activity in disintegrations per second when the activity has decayed to one per cent of its initial value.[1 mark]
  7. 3(b)(vi)State TWO properties of radioactive tracers that make them suitable for use in nuclear imaging.[2 marks]
  8. 3(c)Technetium-99m emits gamma-ray photons of energy 140 keV. Calculate the wavelength of these photons.[4 marks]

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