Evaluation
AQA A-Level Physics 7408
Measurements and Their Errors
Particles and Radiation
Topic overviewConstituents of the atomStable and unstable nucleiParticles, antiparticles and photonsParticle interactionsClassification of particlesQuarks and antiquarksApplications of conservation lawsThe photoelectric effectCollisions of electrons with atomsEnergy levels and photon emissionWave-particle duality
Waves
Mechanics and Materials
Electricity
Further Mechanics and Thermal Physics
Fields and Their Consequences
Topic overviewFieldsNewton's lawGravitational field strengthGravitational potentialOrbits of planets and satellitesCoulomb's lawElectric field strengthElectric potentialCapacitanceParallel plate capacitorEnergy stored by a capacitorCapacitor charge and dischargeMagnetic flux densityMoving charges in a magnetic fieldMagnetic flux and flux linkageElectromagnetic inductionAlternating currentsTransformers
Nuclear Physics
AstrophysicsOptional topic
Topic overviewAstronomical telescope consisting of two converging lensesReflecting telescopesSingle dish radio telescopes, I-R, U-V and X-ray telescopesAdvantages of large diameter telescopesClassification by luminosityAbsolute magnitude, MClassification by temperature, black-body radiationPrinciples of the use of stellar spectral classesThe Hertzsprung-Russell (HR) diagramSupernovae, neutron stars and black holesDoppler effectHubble's lawQuasarsDetection of exoplanets
Medical PhysicsOptional topic
Topic overviewPhysics of visionDefects of vision and their correction using lensesEar as a sound detection systemSensitivity and frequency responseDefects of hearingSimple ECG machines and the normal ECG waveformUltrasound imagingFibre optics and endoscopyMagnetic resonance (MR) scannerThe physics of diagnostic X-raysImage detection and enhancementAbsorption of X-raysCT scannerImaging techniquesHalf-lifeGamma cameraUse of high-energy X-raysUse of radioactive implantsImaging comparisons
Engineering PhysicsOptional topic
Turning Points in PhysicsOptional topic
Topic overviewCathode raysThermionic emission of electronsSpecific charge of the electronPrinciple of Millikan's determination of the electronic charge, eNewton's corpuscular theory of lightSignificance of Young's double slits experimentElectromagnetic wavesThe discovery of photoelectricityWave–particle dualityElectron microscopesThe Michelson-Morley experimentEinstein's theory of special relativityTime dilationLength contractionRelativistic mass and energy
ElectronicsOptional topic
Topic overviewMOSFET (metal-oxide semiconducting field-effect transistor)Zener diodePhotodiodeHall effect sensorDifference between analogue and digital signalsLC resonance filtersThe ideal operational amplifierInverting amplifier configurationNon-inverting amplifier configurationSumming amplifier configurationReal operational amplifiersCombinational logicSequential logicAstablesPrinciples of communication systemsTransmission mediaTime-division multiplexingAmplitude (AM) and frequency modulation (FM) techniques
Measurements and Their Errors
Limitation of physical measurements
- 9 things to know
- Papers 1 and 3
Overview
Random and systematic error, precision and accuracy, and combining absolute and percentage uncertainties.
What you need to know
Answer each one before you reveal it.
Your recallNot started
Evaluation
How is percentage uncertainty found, and how do uncertainties combine when adding?
Evaluation
How do uncertainties combine when quantities are multiplied, divided or raised to a power?
Evaluation
How are the extreme lines of best fit used to find uncertainty in a gradient?
Evaluation
How is gradient uncertainty calculated, what is a zero error, and how can it be corrected?
Evaluation
Why are absolute uncertainties added when two measurements are subtracted?
Evaluation
How do you combine uncertainty for a square root, and how many figures should you quote?
Numbers
When two measurements are multiplied together, how do you combine their uncertainties?
Process
When two measurements are added together, how do you combine their absolute uncertainties?
Questions from this subtopic
Each one with the model answer underneath.
- 1
How do random errors affect readings relative to the true value?
Model answer
Random errors cause readings to scatter unpredictably above and below the true value.
- 2
How can taking repeat measurements help reduce the effect of random errors?
Model answer
Taking repeat measurements allows random errors to partially cancel out, as some readings will be above and some below the true value.
- 3
Why does calculating a mean from repeated measurements reduce random error?
Model answer
Calculating a mean averages out the random scatter, giving a value closer to the true value than any single measurement.
- 4
In what direction do systematic errors shift readings from the true value?
Model answer
Systematic errors shift all readings in the same direction (all too high or all too low) by a consistent amount.
- 5
Can systematic errors be reduced by taking repeat measurements? Explain why.
Model answer
No, because systematic errors affect every reading by the same amount in the same direction, so repeating measurements does not reduce them.
- 6
How can recalibrating an instrument help reduce systematic error?
Model answer
Recalibration adjusts the instrument to give correct readings, removing any consistent offset from the true value.
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