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
X-ray attenuation and imaging
- 4 things to know
- Papers 1, 2 and 3
Overview
Recall 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.
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
How does X-ray intensity vary as the beam passes through an absorbing material?
Questions from this subtopic
Each one with the model answer underneath.
- 1
Define simple scatter as an X-ray attenuation mechanism.
Model answer
Simple scatter is when X-ray photons are deflected by atoms without any energy loss.
- 2
Describe what happens during the photoelectric effect in X-ray attenuation.
Model answer
An X-ray photon is completely absorbed by an atom, causing an inner electron to be ejected.
- 3
Explain the Compton effect as a mechanism of X-ray attenuation.
Model answer
A photon transfers part of its energy to an outer electron and scatters with reduced energy.
- 4
What is pair production in the context of X-ray attenuation?
Model answer
A high-energy photon converts into an electron-positron pair near a nucleus.
- 5
State the equation used to describe X-ray attenuation through a material.
Model answer
I = I₀e^(−μx), where I is transmitted intensity, I₀ is initial intensity, μ is the attenuation coefficient, and x is thickness.
- 6
In the X-ray attenuation equation I = I₀e^(−μx), what does the symbol μ represent?
Model answer
μ represents the attenuation (absorption) coefficient of the material.
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