Uses and risks of radiationIB MYP Physics: Subtopic test

1. 1
   A hospital in Cape Town treats a patient who has a tumour using a beam of gamma rays. The beam is aimed at the tumour from several different directions around the patient's body.

   (a)

   What is this type of treatment called?

   [1 mark]

   • ARadioactive dating
   • BRadiotherapy
   • CFood irradiation
   • DSterilisation

   (b)

   Why is the beam aimed at the tumour from several directions?

   [1 mark]

   • ASo the tumour receives a high dose while healthy tissue along each beam receives a lower dose
   • BSo the gamma rays bend around the healthy tissue
   • CBecause gamma rays cannot pass through skin from one direction
   • DTo make the tumour radioactive

   (c)

   Explain why gamma rays can kill cancer cells.

   [2 marks]

   Total for question 1: 4 marks

2. 2
   A paper mill in Finland makes a continuous sheet of paper that must have a constant thickness. A radioactive source on one side of the moving sheet sends radiation through the paper to a detector on the other side. A computer monitors the count rate at the detector and adjusts the rollers that press the paper.

   (a)

   Which type of radiation is most suitable for monitoring the thickness of the paper?

   [1 mark]

   • AAlpha
   • BGamma
   • CBeta
   • DNone of them

   (b)

   What happens to the count rate at the detector if the paper becomes thicker?

   [1 mark]

   • AIt increases because the paper gives out extra radiation
   • BIt stays the same because the source is constant
   • CIt increases because the paper reflects radiation to the detector
   • DIt decreases because more radiation is absorbed

   (c)

   Explain why a source with a long half-life is chosen for this job.

   [2 marks]

   Total for question 2: 4 marks

3. 3
   A hospital radiographer works with a gamma source for several hours each day. She follows three safety rules: she keeps the source in a lead container when it is not in use, she stays as far from the source as she can, and she limits the time she spends near it. She also wears a film badge.

   (a)

   Explain how each of her three rules reduces the radiation dose she receives.

   [3 marks]

   (b)

   Describe how a film badge works and explain why the radiographer wears one.

   [4 marks]

   Total for question 3: 7 marks

4. 4
   Fruit exporters in Kenya are considering using gamma radiation to kill bacteria and mould on mangoes before they are shipped abroad. The mangoes travel on a conveyor belt past a cobalt-60 source inside a thick concrete chamber. The irradiated mangoes do not become radioactive. Some shoppers are worried about eating irradiated food.

   (a)

   Explain how irradiation makes the mangoes safer and longer lasting, and describe the precautions that protect the workers at the plant.

   [6 marks]

   (b)

   Discuss whether the exporters should use food irradiation, and give a justified conclusion.

   [6 marks]

   Total for question 4: 12 marks

End of questions