Alpha, beta and gamma radiationAQA A-Level Physics: Subtopic test

1. 1
   A factory makes aluminium foil in a continuous strip. A radioactive source is placed on one side of the strip and a Geiger–Müller (GM) tube on the other side. The count rate at the detector is monitored by a computer, which adjusts the rollers that set the thickness of the foil.

   (a)

   Which type of radiation is most suitable for the source used to monitor the thickness of the aluminium foil?

   [1 mark]

   • AAlpha radiation
   • BGamma radiation
   • CNeutron radiation
   • DBeta-minus radiation

   (b)

   The foil leaving the rollers becomes thicker than it should be. What happens to the count rate at the GM tube?

   [1 mark]

   • AIt increases
   • BIt decreases
   • CIt stays the same
   • DIt increases and then decreases

   (c)

   Explain why a gamma source would not be suitable for monitoring the thickness of the aluminium foil.

   [2 marks]

   Total for question 1: 4 marks

2. 2
   A student investigates how the count rate from a gamma source varies with distance. With no source present, a Geiger–Müller (GM) tube records an average of 24 counts per minute. With the source 0.10 m from the tube, the GM tube records 664 counts per minute.

   (a)

   The source is moved to 0.30 m from the tube. What count rate should the student expect from the tube in counts per minute?

   [1 mark]

   • A95
   • B71
   • C213
   • D24

   (b)

   Which graph of corrected count rate C against distance x would be a straight line through the origin if the source obeys the inverse-square law?

   [1 mark]

   • AC against x
   • BC against 1/x
   • CC against 1/x²
   • DC against x²

   (c)

   The student subtracts 24 counts per minute from every reading. Explain why, and give two sources of the radiation responsible for this count.

   [2 marks]

   Total for question 2: 4 marks

3. 3
   A hospital technician handles a sealed gamma source. At a distance of 0.50 m from the source, the gamma intensity is 80 μW m⁻². The source can be treated as a point source in air.

   (a)

   Calculate the intensity of the gamma radiation at a distance of 2.0 m from the source.

   [3 marks]

   (b)

   The technician must work where the intensity is no more than 0.50 μW m⁻². Calculate the minimum distance from the source at which she can work. Explain why she uses long tongs and a lead-lined container when handling the source.

   [4 marks]

   Total for question 3: 7 marks

4. 4
   A hospital radiotherapy department uses a sealed cobalt-60 source, which emits gamma radiation, to treat patients with cancer. Staff also use a laboratory with an unknown sealed source and a Geiger–Müller (GM) tube to teach students about the properties of radiation.

   (a)

   Evaluate the balance of risk and benefit when gamma radiation is used to treat a patient with cancer, and describe measures taken to protect the staff who operate the equipment.

   [6 marks]

   (b)

   Describe how a student could use a GM tube, a stopwatch and absorbers of paper, aluminium and lead to identify the types of radiation emitted by the unknown source. Explain what result would show that the source emits beta radiation only.

   [6 marks]

   Total for question 4: 12 marks

End of questions