AS & A Level Physics 9702 · Topic 24

Medical physics: past paper questions

104 real questionsasked in 8 of the last 10 exam series2019–2025usually: Explain, State, Calculate, Outline, Show

Real questions on medical physics

The newest 20 of 104 written questions. Open one to see it on the real paper.

9702/41 · October/November 2025 · Q10b[2]
Explain how ultrasound waves are detected by a piezoelectric crystal.
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9702/41 · October/November 2025 · Q10c(i)[2]
Calculate the intensity reflection coefficient for ultrasound incident on a water–steel boundary. intensity reflection coefficient =
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9702/41 · October/November 2025 · Q10c(ii)[2]
Explain, without calculation, what is likely to happen when ultrasound is incident on a body tissue–water boundary.
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9702/42 · October/November 2025 · Q10a[1]
State what is meant by contrast in an X-ray image.
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9702/42 · October/November 2025 · Q10b(i)[1]
Show that the intensity of the X-rays emerging in region B is 0.13I 0 . (i)
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9702/42 · October/November 2025 · Q10b(ii)[3]
Determine the linear attenuation coefficient μ of material Q. μ = cm –1
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9702/42 · October/November 2025 · Q10b(iii)[1]
Use the information in (b)(i) to suggest why the X-rays emerging from the structure form an image that has poor contrast.
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9702/42 · October/November 2025 · Q10c[3]
Explain how X-rays are used in computed tomography (CT) scanning to produce a three-dimensional image of an internal structure.
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9702/42 · May/June 2025 · Q6c(i)[3]
Show that the minimum wavelength of these electromagnetic waves is 21 pm.
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9702/42 · May/June 2025 · Q6c(ii)[1]
State the region of the electromagnetic spectrum that contains these waves.
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9702/42 · May/June 2025 · Q6c(iii)[2]
Explain how these electromagnetic waves may be used to form images of internal body structures.
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9702/43 · October/November 2024 · Q9b(i)[3]
Describe how the interaction of a β + particle with an electron in the body enables the formation of an image.
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9702/43 · October/November 2024 · Q9b(ii)[2]
Suggest why 110 minutes is a suitable half-life for a nuclide used as a tracer in medical diagnosis.
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9702/42 · May/June 2024 · Q10a[2]
Describe how reflected ultrasound pulses may be used to obtain diagnostic information about internal structures.
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9702/42 · May/June 2024 · Q10b(i)[2]
Define specific acoustic impedance of a medium.
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9702/42 · May/June 2024 · Q10b(ii)[3]
Table 10.1 shows some data for water and for glass. Table 10.1 density / kg m –3 speed of sound / m s –1 water 1000 1420 glass 2500 4560 Determine the intensity reflection coefficient for ultrasound that is incident on a water–glass boundary. intensity reflection coefficient =
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9702/43 · May/June 2024 · Q8b(ii)[1]
On Fig. 8.1, use + and – signs to label terminals X and Y to indicate the polarity of the high voltage.
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9702/43 · May/June 2024 · Q8c(i)[1]
the maximum energy, in MeV, of an X-ray photon produced at the target maximum photon energy = MeV
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9702/43 · May/June 2024 · Q8c(ii)[2]
the maximum momentum of an X-ray photon produced at the target maximum photon momentum = N s
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9702/43 · May/June 2024 · Q8c(iii)[3]
the minimum wavelength of X-rays produced at the target. minimum wavelength = m
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What examiners said

Many candidates gave part of the answer but not a full answer as to what is meant by a tracer. A significant minority of weaker candidates attempted to describe how a tracer is used rather than answering the question that was asked.
— Examiner report, October/November 2023, 9702/42 Q9(a)(i) (Cambridge)

There was much confusion with other types of medical imaging in responses seen to this question, with image formation in ultrasound scanning and CT scanning being commonly discussed.
— Examiner report, October/November 2023, 9702/42 Q9(b)(ii) (Cambridge)

A common mistake here was to forget the central dark circle which will always be there no matter what the speed of the electrons.
— Examiner report, May/June 2023, 9702/41 Q7(c)(i) (Cambridge)

Practise this topic

Answer these questions online and get each one marked against the official mark scheme, with what you missed and how to fix it.

Practise medical physics

In the syllabus

24.1 Production and use of ultrasound

understand that a piezo-electric crystal changes shape when a p.d. is applied across it and that the
understand how ultrasound waves are generated and detected by a piezoelectric transducer
understand how the reflection of pulses of ultrasound at boundaries between tissues can be used to
define the specific acoustic impedance of a medium as Z = ρc, where c is the speed of sound in the
use IR / I0 = (Z1 – Z2)2 / (Z1 + Z2)2 for the intensity reflection coefficient of a boundary between two media
recall and use I = I0e –μ x for the attenuation of ultrasound in matter

24.2 Production and use of X-rays

explain that X-rays are produced by electron bombardment of a metal target and calculate the minimum
understand the use of X-rays in imaging internal body structures, including an understanding of the
recall and use I = I0e –μ x for the attenuation of X-rays in matter
understand that computed tomography (CT) scanning produces a 3D image of an internal structure

24.3 PET scanning

understand that a tracer is a substance containing radioactive nuclei that can be introduced into the
recall that a tracer that decays by β+ decay is used in positron emission tomography (PET scanning)
understand that annihilation occurs when a particle interacts with its antiparticle and that mass–energy
explain that, in PET scanning, positrons emitted by the decay of the tracer annihilate when they interact
calculate the energy of the gamma-ray photons emitted during the annihilation of an electron-positron
understand that the gamma-ray photons from an annihilation event travel outside the body and can

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