Process
OCR A-Level Physics A H556
Practical Skills in the Written Papers
The Practical Endorsement
Topic overviewAnalogue and digital measuring instrumentsImproving accuracy with repeat timing, fiducial markers and plumb linesTiming, calipers and micrometersConstructing and testing circuitsSignal generators and oscilloscopesGenerating and measuring wavesData loggers, modelling software and ionising radiation
Physical Quantities and Units
Making Measurements and Analysing Data
Nature of Quantities
Motion
Forces in Action
Work, Energy and Power
Materials
Newton’s Laws of Motion and Momentum
Charge and Current
Energy, Power and Resistance
Electrical Circuits
Waves
Topic overviewProgressive waves and their propertiesThe wave equationReflection, refraction and diffractionWave graphs and intensityThe electromagnetic spectrumPolarisationRefraction and refractive indexCritical angle and total internal reflectionThe principle of superpositionInterference, coherence and path differenceTwo-source interference, Young's double-slit experiment and the diffraction gratingForming stationary wavesStationary waves on strings and in air columnsMeasuring the speed of soundNode spacing, amplitude and phase in stationary wavesHarmonics and the fundamental mode
Quantum Physics
Thermal Physics
Topic overviewThermal equilibrium and absolute temperatureThe kinetic model of solids, liquids and gasesBrownian motion and internal energySpecific heat capacityMeasuring specific heat capacitySpecific latent heatMeasuring specific latent heatMoles, the Avogadro constant and kinetic theoryGas laws, the ideal gas equation and r.m.s. speedMaxwell-Boltzmann distribution, Boltzmann constant and internal energy
Oscillations
Gravitational Fields
Astrophysics and Cosmology
Topic overviewThe solar system and the birth of a starThe death of a low-mass starSupernovae, neutron stars and black holesThe Hertzsprung-Russell diagramEnergy levels and emission spectraAbsorption spectra and spectral linesPhoton energy and the diffraction gratingWien's law and Stefan's lawAstronomical distances, parallax and the cosmological principleDoppler shift and Hubble's lawThe expanding universe and the Big BangEvidence for the Big Bang and dark energy
Capacitors
Topic overviewCapacitance and charging a capacitorCapacitors in seriesCapacitors in parallel and combined circuitsEnergy stored by a capacitorCharging and discharging through a resistorInvestigating capacitor dischargeThe time constantIterative modelling, exponential decay and the constant-ratio property
Electric Fields
Electromagnetism
Nuclear and Particle Physics
Topic overviewAlpha-particle scattering and the nuclear modelProton number, nucleon number and isotopesThe strong nuclear force and nuclear radiusParticles, antiparticles and hadronsLeptons and the quark modelQuark composition and chargesBeta decay in the quark modelRadioactive decay and the three radiationsNuclear decay equationsActivity, decay constant and half-lifeExponential decay and radioactive datingMass-energy equivalenceAnnihilation, mass defect and binding energyBinding energy per nucleon and induced fissionThe fission reactor and nuclear wasteNuclear fusion and balancing nuclear equations
Medical Imaging
- 8 subtopics
- 24 things to know
- Papers 1, 2 and 3
What Medical Imaging covers
Physics applied to diagnosis: how X-rays are produced and attenuated, CAT scanning, the gamma camera and PET, and ultrasound including the Doppler technique.
Where it is assessed
Papers 1, 2 and 3
Newtonian world, astrophysics and particles, drawn on across the papers.
Check the OCR specification ↗The 8 subtopics
Each one has its own page.
- The X-ray tubeRecall questions on the heated filament, target and accelerating potential difference, and how X-ray photons are produced.Open →
- X-ray attenuation and imagingRecall questions on simple scatter, the photoelectric effect, Compton effect and pair production, the attenuation equation I = I₀e^(−μx), how intensity falls through an absorber, and barium and iodine contrast media.Open →
- CAT scanningRecall questions on how a CAT scanner collects and reconstructs X-ray data, and its advantages over conventional X-ray images for depth, soft tissue contrast and small density differences.Open →
- Medical tracers and the gamma cameraRecall questions on technetium-99m as a tracer, the collimator, scintillator, photomultiplier tubes and computer of a gamma camera, diagnosing organ function, and the costs of expensive scanners.Open →
- PET scanningRecall questions on positron-electron annihilation, fluorine-18 tracers, 511 keV gamma photons, coincidence detection and lines of response, forming PET images, uses in cancer and neurology, and cyclotron supply.Open →
- Ultrasound and the piezoelectric transducerRecall questions on the piezoelectric effect, ultrasound frequencies, how a transducer emits and detects ultrasound, and A-scans and B-scans.Open →
- Acoustic impedance and reflectionRecall questions on Z = ρc, the fraction of intensity reflected at a boundary, and why a coupling gel is needed.Open →
- Doppler ultrasoundRecall questions on the Doppler effect in ultrasound, the Doppler equation for blood speed with calculations, the factor of 2 and why the beam must be angled to the blood flow.Open →
What you need to know
Answer each one before you reveal it.
Your recallNot started
Process
What is pair production in X-ray attenuation, and what happens to the electrons and their kinetic energy when they reach the target metal of an X-ray tube?
Numbers
State the X-ray attenuation equation, describe how X-ray intensity varies through the material, and state what μ represents.
Key term
Explain how a gamma camera forms an image of tracer distribution within a patient.
Key term
Define the term 'line of response' in PET scanning, and explain how lines of response are used to form a three-dimensional image.
Key term
In Doppler ultrasound, what does the angle θ represent and what is the Doppler effect, and how does coupling gel reduce reflection at the skin?
Key term
Why might a hospital with a PET scanner require an on-site cyclotron or rapid delivery service?
Key term
How is acoustic impedance of a medium defined?
Process
What component in an X-ray tube acts as the cathode, and by what process does it release electrons?
Key term
How are electrons initially produced in an X-ray tube?
Key term
How does X-ray intensity vary as the beam passes through an absorbing material?
Key term
What type of X-ray beam does the rotating X-ray tube in a CAT scanner produce?
Key term
What type of radiation does technetium-99m emit, and what is its approximate half-life?
Key term
What type of wave is ultrasound classified as?
Key term
What frequency range defines ultrasound?
Numbers
State the equation used to calculate acoustic impedance.
Key term
What is the piezoelectric effect?
Key term
What is the function of the anode in an X-ray tube?
Key term
How are X-ray transmission measurements collected in a CAT scanner?
Key term
What is the role of the scintillator in a gamma camera, and what material is typically used?
Key term
What type of decay does fluorine-18 undergo, and what is its approximate half-life?
Key term
How does an ultrasound transducer emit ultrasound waves?
Numbers
Calculate the acoustic impedance when density = 1570 kg m⁻³, speed of sound = 3000 m s⁻¹.
Key term
What is the Doppler effect in the context of ultrasound imaging?
Take Medical Imaging further
The same content, four other ways.
Commonly confused
Pairs that lose marks when they are blurred together.
A-scan vs B-scan
A-scan: one-dimensional echo-amplitude display. 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.
Tracer vs Contrast medium
Tracer: radioactive substance followed through the body. Contrast medium: non-radioactive substance improving image contrast.
Questions from this topic
Each one with the model answer underneath.
- 1
What component in an X-ray tube acts as the cathode, and by what process does it release electrons?
Model answer
A heater acts as the cathode, releasing electrons by thermionic emission.
- 2
How are electrons initially produced in an X-ray tube?
Model answer
Electrons are emitted from the heated cathode by thermionic emission.
- 3
What is the function of the anode in an X-ray tube?
Model answer
The anode is a positive electrode that accelerates electrons towards the target metal.
- 4
What property must the target metal in an X-ray tube have, and what is its role?
Model answer
The target metal must have a high atomic number; electrons strike it to produce X-rays.
- 5
What is the purpose of the high voltage supply in an X-ray tube, and what typical voltage range is used?
Model answer
It accelerates electrons from cathode to anode, typically using tens to hundreds of kilovolts.
- 6
What causes the electrons in an X-ray tube to gain high speeds before reaching the target?
Model answer
Electrons are accelerated by the high voltage applied across the tube.
What is inside Levo
Six ways to work the same material.
Medical Imaging revision questions
- What does Medical Imaging cover in OCR A-Level Physics A?
- 8 subtopics: the x-ray tube, x-ray attenuation and imaging, cat scanning, medical tracers and the gamma camera, pet scanning, ultrasound and the piezoelectric transducer, acoustic impedance and reflection and doppler ultrasound. Each one has its own page with questions and model answers.
- How is Medical Imaging organised?
- By the OCR H556 specification, subtopic by subtopic, so it matches the order you are taught it in.
Every question in Medical Imaging, on a schedule.
Attempt a question from memory, write the correct version, then attempt it again. Levo records the jump between your first attempt and your last, and brings each question back on the day you are due to forget it.
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