Medical Physics

What Medical Physics covers

Medical physics is one of the five optional topics, sat on Paper 3. It applies optics, sound and radiation physics to the body: how the eye and ear work and how their defects are corrected, then the imaging techniques built on ultrasound, X-rays, magnetic resonance and gamma emission.

The 19 subtopics

Each one has its own page.

• Physics of visionRefraction at the cornea and lens, accommodation, the retina, and rod and cone vision.Open →
• Defects of vision and their correction using lensesLens power in dioptres, the lens equation, and correcting myopia and hypermetropia.Open →
• Ear as a sound detection systemThe outer, middle and inner ear, pressure amplification by the ossicles, and the cochlea.Open →
• Sensitivity and frequency responseSound intensity, the decibel and dBA scales, and equal loudness curves.Open →
• Defects of hearingNoise-induced and age-related hearing loss, and how each appears on an audiogram.Open →
• Simple ECG machines and the normal ECG waveformDetecting and amplifying the heart's electrical signal, and the P, QRS and T features.Open →
• Ultrasound imagingAcoustic impedance, the reflection coefficient, coupling gel, and A-scans and B-scans.Open →
• Fibre optics and endoscopyTotal internal reflection, coherent and non-coherent bundles, and the advantages of endoscopy.Open →
• Magnetic resonance (MR) scannerThe superconducting magnet, gradient coils, RF excitation of protons, and the relaxation signal.Open →
• The physics of diagnostic X-raysX-ray production, the continuous and characteristic spectra, and controlling intensity and energy.Open →
• Image detection and enhancementFlat panel detectors, intensifying screens and image intensifiers for X-ray imaging, and how a barium meal uses an X-ray opaque material to enhance contrast in images of the gut.Open →
• Absorption of X-raysThe exponential attenuation equation, the attenuation coefficients, and half-value thickness.Open →
• CT scannerHow a CT image is reconstructed, and the dose and cost weighed against the detail gained.Open →
• Imaging techniquesThe tracers used in nuclear medicine, what makes a good one, and the technetium generator.Open →
• Half-lifePhysical, biological and effective half-life, and the formula relating them.Open →
• Gamma cameraThe collimator, scintillator and photomultiplier, and how an image is built up.Open →
• Use of high-energy X-raysExternal radiotherapy, why the source is rotated, and why cancer cells are more vulnerable.Open →
• Use of radioactive implantsBrachytherapy, why beta emitters are used, and the short range of the radiation.Open →
• Imaging comparisonsWeighing X-ray, CT, ultrasound, MRI and PET on resolution, dose, cost and availability.Open →

What you need to know

Answer each one before you reveal it.

Take Medical Physics further

The same content, four other ways.

Commonly confused

Pairs that lose marks when they are blurred together.

• Absorbed dose vs Equivalent dose

  Absorbed dose: energy deposited per unit mass. Equivalent dose: energy deposition weighted for radiation type.

• Ultrasound A-scan vs Ultrasound B-scan

  Ultrasound A-scan: one-dimensional echo-amplitude display. Ultrasound B-scan: two-dimensional brightness image.

• Computed tomography vs Magnetic resonance imaging

  Computed tomography: cross-sectional imaging using multiple X-ray projections. Magnetic resonance imaging: imaging using nuclear resonance in magnetic fields.

Questions from this topic

Each one with the model answer underneath.

1. 1

   Which structure in the eye provides the majority of the refractive power?

   Model answer

   The cornea provides most of the refractive power.

2. 2

   What is the role of the lens in the eye's optical system?

   Model answer

   The lens adjusts focus for objects at different distances by fine-tuning the refraction of light.

3. 3

   Where does the image form in the eye after light has been refracted?

   Model answer

   The image forms on the retina.

4. 4

   At which surface does light first undergo significant refraction when entering the eye?

   Model answer

   Light is first refracted at the cornea surface.

5. 5

   After passing through the cornea, where does light undergo further refraction before reaching the retina?

   Model answer

   Light is further refracted at the surfaces of the lens.

6. 6

   In a ray diagram of the eye viewing a distant object, what do the incident parallel rays represent?

   Model answer

   Parallel rays represent light from a distant object, where the rays are effectively parallel due to the large object distance.

What is inside Levo

Six ways to work the same material.

Medical Physics revision questions

What does Medical Physics cover in AQA A-Level Physics?

19 subtopics: physics of vision, defects of vision and their correction using lenses, ear as a sound detection system, sensitivity and frequency response, defects of hearing, simple ecg machines and the normal ecg waveform, ultrasound imaging, fibre optics and endoscopy, magnetic resonance (mr) scanner, the physics of diagnostic x-rays, image detection and enhancement, absorption of x-rays, ct scanner, imaging techniques, half-life, gamma camera, use of high-energy x-rays, use of radioactive implants and imaging comparisons. Each one has its own page with questions and model answers.

How is Medical Physics organised?

By the AQA 7408 specification, subtopic by subtopic, so it matches the order you are taught it in.