1. 1
   A hospital physicist is training new radiographers on the basics of atomic structure before they begin working with radioactive tracers used in medical imaging. She uses the notation $^{14}_{6}\text{C}$ to represent a nucleus of carbon-14, and explains that isotopes of the same element always have the same atomic number but can have different mass numbers.

   (a)

   A hospital physicist is explaining atomic structure to trainee radiographers using the nucleus of carbon-14, written as $^{14}_{6}\text{C}$. Which row correctly states the number of protons and the number of neutrons in this nucleus?

   [1 mark]

   • A6 protons, 8 neutrons
   • B6 protons, 14 neutrons
   • C8 protons, 6 neutrons
   • D14 protons, 6 neutrons

   (b)

   The physicist explains that carbon-12 and carbon-14 are isotopes of the same element. Which statement correctly describes what this means?

   [1 mark]

   • AThey have the same number of neutrons but different numbers of protons
   • BThey have the same number of protons but different numbers of neutrons
   • CThey have different numbers of protons and different numbers of neutrons
   • DThey have the same number of protons and the same number of neutrons

   (c)

   Describe the structure of an atom in terms of the three particles it contains, stating where each particle is located.

   [2 marks]

   Total for question 1: 4 marks

2. 2
   An archaeologist is investigating a sealed stone burial chamber, over a metre thick in places, and wants to understand why a Geiger-Muller detector placed outside the chamber only registers a very weak signal above background level, despite instruments inside detecting a much stronger source.

   (a)

   An archaeologist is examining a sealed stone chamber and wants to identify which type of radiation, if any, could pass through the thick stone wall to be detected outside. Which type of radiation has the greatest penetrating power through a thick solid barrier?

   [1 mark]

   • AInfrared radiation
   • BAlpha particles
   • CBeta particles
   • DGamma rays

   (b)

   Inside the chamber, the archaeologist's detector registers ionising radiation from a decaying source. Which property is shared by alpha, beta and gamma radiation?

   [1 mark]

   • AThey are all deflected in the same direction by a magnetic field
   • BThey all have the same penetrating power
   • CThey are all emitted from unstable nuclei in a random process
   • DThey all consist of charged particles

   (c)

   Explain, in terms of ionising ability and penetrating power, why alpha particles emitted inside the chamber are very unlikely to be detected outside it, even though they are the most strongly ionising of the three radiation types.

   [2 marks]

   Total for question 2: 4 marks

3. 3
   A nuclear engineer at a research facility is documenting the decay of several radioactive samples used in student demonstrations, and must write balanced nuclear equations to show exactly how the identity of each nucleus changes as it emits radiation.

   (a)

   A radioactive source undergoes beta decay, and a nuclear engineer needs to write a balanced nuclear equation to record the change. Explain how the atomic number and mass number of a nucleus change when it emits a beta particle, and how a nuclear equation is balanced to show this.

   [3 marks]

   (b)

   One of the samples emits an alpha particle. A nucleus of radium-226 (atomic number 88) decays by alpha emission. State the mass number and atomic number of the new nucleus formed, and explain, using the structure of an alpha particle, why these values change as they do.

   [4 marks]

   Total for question 3: 7 marks

4. 4
   A school physics department is planning a series of practical demonstrations to help students understand how the different types of nuclear radiation can be identified and detected, using both electronic and traditional methods available in a typical school laboratory.

   (a)

   A school physics department is designing a practical to investigate the penetrating powers of alpha, beta and gamma radiation using sealed sources and a Geiger-Muller tube, with absorbers of paper, aluminium sheet and thick lead placed between the source and detector in turn. Describe how the practical should be carried out and what results would be expected for each absorber, and explain how photographic film could be used as an alternative method of detecting these radiations.

   [6 marks]

   (b)

   The department also wants students to understand why the isotope chosen for a particular use, such as a smoke detector, medical tracer or industrial thickness gauge, must be matched to both its type of radiation and its half-life. Explain, with reference to at least two different applications, why the type of radiation emitted and the half-life of the isotope are both important factors in choosing a suitable source, and discuss the safety precautions that must be taken when handling and disposing of such sources.

   [6 marks]

   Total for question 4: 12 marks

End of questions