Lesson 3.10

3.10 Medical physics: eye, ear, ECG, imaging and radionuclides Quiz: AQA Physics, Unit 10

20 questions

Written by Revision Ninja · Last reviewed 11 October 2026

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Lesson 3.10, Medical physics: eye, ear, ECG, imaging and radionuclides: 20 multiple choice questions for the AQA Physics (7408), Unit 10: Medical physics (A-level option), written with Revision Ninja.

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The 20 questions

  1. What is the difference between cone and rod cells in the eye, in terms of spatial resolution and light sensitivity?

    • rods alone give the highest spatial resolution in all light conditions
    • cones are only found in the peripheral retina and do not affect resolution
    • cones give high spatial resolution and colour vision in bright light, while rods are more sensitive in dim light but give poorer resolution
    • rods give colour vision and cones are more sensitive in dim light

  2. What is the power of a lens with focal length f, in dioptres?

    • P = 1/f squared, with f in metres
    • P = f squared, with f in metres
    • P = 1/f, with f in metres
    • P = f, with f in centimetres

  3. How is myopia (short-sightedness) corrected?

    • with a cylindrical lens of positive power
    • with a prism that bends light towards the nose
    • with a converging (convex) lens
    • with a diverging (concave) lens

  4. How is hypermetropia (long-sightedness) corrected?

    • with a converging (convex) lens
    • with a diverging (concave) lens
    • with a cylindrical lens only
    • with no lens, since it is a problem with the retina

  5. A converging lens has focal length 0.25 m. What is its power?

    • -4.0 D
    • 0.25 D
    • 2.5 D
    • 4.0 D

  6. An object is 0.50 m from a converging lens of focal length 0.20 m. Where is the image formed?

    • 0.20 m from the lens on the other side
    • 0.14 m from the lens on the other side
    • 0.33 m from the lens on the other side
    • 0.50 m from the lens on the other side

  7. A sound has an intensity of 1.0 x 10^-6 W m^-2. What is its intensity level, using I0 = 1.0 x 10^-12 W m^-2?

    • 6 dB
    • 120 dB
    • 0.6 dB
    • 60 dB

  8. By how much does the intensity level of a sound rise when its intensity doubles?

    • 2 dB
    • 6 dB
    • 10 dB
    • about 3 dB

  9. A sound is 30 dB louder than a reference sound. What is the ratio of their intensities?

    • 30
    • 10
    • 1000
    • 300

  10. Two tissues have acoustic impedances in the ratio Z1 = 1.5 and Z2 = 4.5 (arbitrary units). What fraction of intensity is reflected at the boundary?

    • 0.25
    • 0.75
    • 0.125
    • 0.50

  11. A soft tissue has density 1000 kg m^-3 and speed of ultrasound 1500 m s^-1. What is its acoustic impedance?

    • 1.5 x 10^9 kg m^-2 s^-1
    • 1.5 x 10^3 kg m^-2 s^-1
    • 6.7 x 10^-7 kg m^-2 s^-1
    • 1.5 x 10^6 kg m^-2 s^-1

  12. What does the P wave on a normal ECG waveform represent?

    • atrial repolarisation at the start of the cycle
    • atrial depolarisation, which precedes atrial contraction
    • ventricular depolarisation, which is the QRS complex
    • ventricular repolarisation, which is the T wave

  13. Which part of a normal ECG corresponds to ventricular depolarisation?

    • the PR segment
    • the T wave
    • the P wave
    • the QRS complex

  14. What condition is needed for total internal reflection in an optical fibre core?

    • the cladding has a higher refractive index than the core
    • light passes from air directly into the core
    • light strikes the core-cladding boundary at normal incidence
    • light travels from the core towards the cladding, with the core having a higher refractive index and the angle exceeding the critical angle

  15. An X-ray tube operates at 80 kV. What is the maximum photon energy produced?

    • 160 keV
    • 80 keV
    • 40 keV
    • 8 keV

  16. A material has a linear attenuation coefficient of 0.50 per cm. What is its half-value thickness?

    • 1.4 cm
    • 0.35 cm
    • 2.0 cm
    • 0.69 cm

  17. A technetium-99m tracer has half-life 6 hours. What fraction of the activity remains after 18 hours?

    • one sixth
    • one eighth
    • one quarter
    • one half

  18. A radioisotope has a physical half-life of 8 days and a biological half-life of 12 days. What is its effective half-life?

    • 10 days
    • 2.4 days
    • 4.8 days
    • 20 days

  19. What does a photomultiplier tube do in a gamma camera?

    • it converts gamma rays directly into sound waves
    • it stores the image for later display on a screen
    • it converts the weak light flashes from a scintillator into an amplified electrical pulse
    • it focuses gamma rays onto a lens to form an image

  20. Which imaging technique gives good soft-tissue resolution without using ionising radiation?

    • PET scanning, which uses positron-emitting tracers
    • MRI scanning, which uses non-ionising radio frequency fields
    • CT scanning, which uses X-rays
    • gamma camera imaging with technetium-99m

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