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1 markRadioactivity

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

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.

Express the activity in disintegrations per second when the activity has decayed to one per cent of its initial value.

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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)(iv)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…[4 marks]
  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