1. 1
   A household smoke detector contains a small sealed source that emits alpha radiation continuously into a small ionisation chamber. The alpha particles ionise air molecules inside the chamber, allowing a tiny current to flow; smoke entering the chamber disrupts this current and triggers the alarm.

   (a)

   A household smoke detector contains a small source that emits alpha radiation to ionise air inside the detector. What is an alpha particle?

   [1 mark]

   • AA high-speed electron
   • BA packet of electromagnetic energy from the nucleus
   • CTwo protons and two neutrons
   • DA single neutron

   (b)

   Why is it safe to keep an alpha-emitting source permanently sealed inside a smoke detector in a home?

   [1 mark]

   • AAlpha radiation has the weakest ionising power of the three types of nuclear radiation
   • BAlpha radiation is not ionising and cannot damage cells
   • CAlpha radiation can travel through several metres of concrete
   • DAlpha radiation has a very short range in air and is easily absorbed by the detector's casing

   (c)

   Explain why alpha radiation is strongly ionising but has only a short range in air, in terms of the properties of an alpha particle.

   [2 marks]

   Total for question 1: 4 marks

2. 2
   A hospital radiographer regularly operates an X-ray machine, standing behind a lead screen for protection, and also wears a radiation dosimeter badge to monitor total exposure over time, including background radiation received outside work.

   (a)

   A hospital radiographer stands behind a lead screen while operating an X-ray machine, rather than remaining in the room with the patient. Which term describes what happens to the radiographer if some radiation were to reach them through gaps in the shielding?

   [1 mark]

   • AContamination
   • BFission
   • CIrradiation
   • DFusion

   (b)

   Alongside radiation from medical equipment, the radiographer's dosimeter also records background radiation received from natural sources. Which of these is a natural source of background radiation?

   [1 mark]

   • ARadiotherapy equipment
   • BNuclear power station coolant
   • CSmoke detectors
   • DCosmic rays from space

   (c)

   Explain the difference between radioactive contamination and irradiation, using the radiographer's situation to illustrate your answer.

   [2 marks]

   Total for question 2: 4 marks

3. 3
   Archaeologists are dating a wooden artefact by measuring the count rate of a radioactive isotope it contains, and comparing it with the count rate the same mass of fresh material would have shown when the artefact was made.

   (a)

   Archaeologists find that a sample of material originally contained a count rate of 480 counts per minute from a radioactive isotope, which has now fallen to 60 counts per minute. Given that the isotope has a half-life of 5730 years, calculate the age of the sample.

   [3 marks]

   (b)

   The isotope in the artefact decays by beta emission. Balance the following nuclear equation for this decay, giving the mass number and atomic number of the daughter nucleus X: $^{14}_{6}\text{C} \rightarrow \ ^{A}_{Z}\text{X} + \ ^{0}_{-1}\beta$

   [4 marks]

   Total for question 3: 7 marks

4. 4
   A company plans to build a long-term underground storage facility for radioactive waste from several different sources, and engineers must design suitable shielding and handling procedures to protect the workers who will manage the facility over many decades.

   (a)

   A company plans to build a long-term storage facility for radioactive waste, and must choose shielding materials to protect nearby workers. Compare the ionising power, penetration through materials and range in air of alpha, beta and gamma radiation, and use this to explain what shielding would be needed to protect workers from each type.

   [6 marks]

   (b)

   The facility will store both a waste product with a short half-life and one with a very long half-life. Evaluate how the half-life of each waste product affects the hazard it poses to workers and the precautions needed when handling and storing it.

   [6 marks]

   Total for question 4: 12 marks

End of questions