Key term
WJEC A-Level Physics 1420QS
Basic Physics
Kinematics
Dynamics
Energy Concepts
Solids Under Stress
Using Radiation to Investigate Stars
Particles and Nuclear Structure
Topic overviewQuarks, leptons and hadronsThe four interactions and conservation lawsThe first generation of quarks and leptonsAntiparticles and annihilationBaryons, antibaryons and mesonsDeducing quark compositions from chargeBeta decay and quark flavour changeTesting a reaction against the conservation rules
Conduction of Electricity
Resistance
Topic overviewCalculating resistance from resistivityPotential difference, Ohm's law and powerResistivity, temperature and superconductivityThe volt: energy transferred per unit chargeCurrent–voltage characteristics of non-ohmic componentsMeasuring resistance and resistivity in the laboratoryThe heating effect of a current and choosing a power equationThermistors and how a semiconductor's resistance falls with temperatureConductance, conductivity and comparing materials
D.C. Circuits
Topic overviewKirchhoff's laws, and resistors in series and parallelPotential dividers, emf and internal resistanceCells, resistivity, power and energyWorking out currents and potential differences in resistor networksSensor circuits with thermistors and LDRsInternal resistance, power transfer and short-circuit currentAmmeters, voltmeters and their effect on the circuit
The Nature of Waves
Wave Properties
Topic overviewEnergy transfer and the wave equationTransverse and longitudinal waves, path difference and intensityDiffraction and superpositionTwo-source interference and the diffraction gratingStationary wavesHow much a wave spreads at a gap or an obstacleCoherence and the conditions for observable interferenceYoung's double slit and λ = ay/DMeasuring wavelength with a diffraction gratingMeasuring the speed of sound with stationary waves
Refraction of Light
Photons
Topic overviewPhoton energy and the electronvoltThe photoelectric effectStopping potential and the Planck constantThe photoelectric effect and photon energiesLine spectra and energy levelsDemonstrating the photoelectric effectThe electromagnetic spectrum and typical photon energiesElectron diffraction and the de Broglie relationshipRadiation pressure
Lasers
Circular Motion
Vibrations
Topic overviewSimple harmonic motion and its equationsOscillating systems and energyDamping and resonanceThe simple pendulumThe mass–spring oscillatorThe displacement and velocity equationsGraphs of displacement, velocity and accelerationThe energy interchange in simple harmonic motionFree and forced oscillationsLight, heavy and critical damping
Kinetic Theory
Thermal Physics
Topic overviewInternal energy and heatWork, the first law and specific heat capacityThermal equilibrium, temperature and absolute zeroThe internal energy of an ideal monatomic gasWork done by a gas at constant pressureThe p–V diagram and work as an areaSign conventions and special cases of the first lawMeasuring specific heat capacity
Nuclear Decay
Nuclear Energy
Capacitance
Topic overviewCapacitance and the parallel plate capacitorEnergy, combinations and RC circuitsCharging at constant current and measuring capacitanceDielectrics and relative permittivityThe uniform field between capacitor platesEnergy stored in a capacitor and the Q–V graphExponential discharge, the time constant and log graphsCapacitors in series and parallel: charge and potential difference sharing
Electrostatic and Gravitational Fields of Force
Topic overviewElectric and gravitational fields comparedField lines, equipotentials and combining fieldsElectric potential and the work done on a chargeGravitational potential and potential energyAdding potentials and fields from several sourcesEquipotential surfacesComparing the two fields point by point
Orbits and the Wider Universe
Topic overviewKepler's laws and orbital motionThe Doppler effect, dark matter and the expanding universeNewton's law of gravitation applied to orbitsDeriving Kepler's third lawFinding the mass of a central objectGalactic rotation curves and dark matterThe centre of mass of a two-body systemRadial velocity and the Doppler shift of spectral linesHubble's law and the age of the universe
Magnetic Fields
Topic overviewMagnetic fields and field patternsMagnetic flux density and the force on a conductorThe force on a moving charge and its circular pathThe Hall effect and the Hall voltageMagnetic fields due to a current in a wire and in a solenoidForces between current-carrying conductorsCharged particle beams, velocity selectors and accelerators
Electromagnetic Induction
Option A: Alternating CurrentsOption A
Option B: Medical PhysicsOption B
Topic overviewMedical physicsUltrasound imagingRadiation and living tissueX-ray production and beam controlAttenuation and half-value thicknessRadiography, fluoroscopy and CT scanningAcoustic impedance and ultrasound reflectionMagnetic resonance imagingAbsorbed dose, equivalent dose and effective doseRadionuclide tracers, the gamma camera and PET
Option C: The Physics of SportsOption C
Topic overviewCentre of gravity, stability and momentsRestitution, moment of inertia and angular momentumRotational energy, projectiles and the flight of a ballMoments in the muscles and jointsApplying the impulse equation in sportMoment of inertia and angular kinematicsTorque, angular momentum and its conservationRotational energy and energy conservation in sport
Option D: Energy and the EnvironmentOption D
Topic overviewFactors affecting the rate at which the temperature of the Earth risesThe Earth's thermal equilibrium, Wien's law and Stefan's lawRenewable and non-renewable sourcesSolar energy and photovoltaic cellsWind, tidal and hydroelectric powerNuclear fission and fusion as energy sourcesU-values and rates of heat lossFuel cells and how they workFuel cells: benefits, limitations and the hydrogen economyThermal conduction, conductivity and insulation
Mathematical Requirements (Appendix C)
Topic overviewSignificant figures and arithmetic meansUncertainty and how uncertainties combineAlgebraic symbols and proportionalityRearranging and solving equationsSmall angle approximationsTangents and instantaneous rates of changeAreas under curves and numerical methodsReading a tangent on a motion graphStraight-line graphs and y = mx + cWhat a gradient and an intercept representLinearising a relationship to find a constantLog plots of exponential decayChoosing what to plot to find a constantLogarithmic scales and orders of magnitudeWorking with base-ten logarithmsThe shapes of common graphsInverse and root relationships on a graphAreas, volumes and PythagorasGeometry applied to physical situationsSubstituting into physical equationsTrigonometry and right-angled trianglesResolving a force into componentsRadians, arc length and force diagramsRandom processes and translating between representationsMean values and periodic functionsSymbols for approximation and comparison
Nuclear Decay
- 6 subtopics
- 18 things to know
- A2 Unit 3
What Nuclear Decay covers
Nuclear Decay is examined on A2 Unit 3 of WJEC Physics, Oscillations and Nuclei. 90 recall questions across 6 subtopics.
The 6 subtopics
Each one has its own page.
- Radioactive decay, activity and half-lifeRecall questions on Radioactive decay, activity and half-life.Open →
- Distinguishing the radiations, and background radiationRecall questions on Distinguishing the radiations and background radiation.Open →
- Randomness and spontaneity in radioactive decayRecall questions on Randomness and spontaneity in radioactive decay.Open →
- Writing and balancing nuclear decay equationsRecall questions on Writing and balancing nuclear decay equations.Open →
- The decay constant and activityRecall questions on The decay constant and activity.Open →
- The exponential decay law in calculationsRecall questions on The exponential decay law in calculations.Open →
What you need to know
Answer each one before you reveal it.
Your recallNot started
Key term
What is the activity of a radioactive source, and how is it measured?
Key term
In the equation A = λN, what does each symbol represent?
Key term
Explain how repeatedly throwing a large number of dice and removing every six models radioactive decay.
Numbers
Cobalt-60 has a half-life of 5.27 years. Calculate its decay constant in s⁻¹, taking one year as 3.16 × 10⁷ s.
Key term
State the nature of alpha radiation.
Key term
What is meant by saying that radioactive decay is spontaneous?
Key term
Explain what each part of the notation ᴬZX represents.
Key term
How do the nucleon number and proton number change when a nucleus emits an α particle?
Key term
State the unit of the decay constant.
Key term
State the exponential decay law written in terms of activity.
Key term
State the form of the decay law that uses the number of half-lives elapsed.
Key term
Define the activity of a radioactive source.
Key term
State the nature of beta-minus radiation.
Key term
Explain why heating a radioactive source does not change its activity.
Key term
How do the nucleon number and proton number change in β⁻ decay?
Key term
State the equation linking activity, decay constant and number of undecayed nuclei, defining each symbol with its unit.
Key term
Must the number of half-lives x be a whole number?
Take Nuclear Decay further
The same content, four other ways.
Commonly confused
Pairs that lose marks when they are blurred together.
Activity vs The decay constant
Activity: the number of nuclei decaying per unit time. The decay constant: the probability that any one nucleus decays per unit time.
Half-life vs Background radiation
Half-life: the time for the number of undecayed nuclei to fall by half. Background radiation: the ionising radiation always present from the environment.
Questions from this topic
Each one with the model answer underneath.
- 1
What is meant by radioactive decay being a random process?
Model answer
It is impossible to predict which particular nucleus will decay next; each nucleus has an equal probability of decaying in any given time interval.
- 2
Why do unstable nuclei undergo radioactive decay?
Model answer
To become more stable by emitting radiation.
- 3
What does it mean that radioactive decay is spontaneous?
Model answer
It cannot be predicted exactly when a particular nucleus will decay; the decay occurs without any external trigger.
- 4
Define the activity of a radioactive source.
Model answer
The number of nuclei decaying per unit time.
- 5
What is the SI unit of activity?
Model answer
The becquerel (Bq).
- 6
What does one becquerel represent?
Model answer
One decay per second.
What is inside Levo
Six ways to work the same material.
Nuclear Decay revision questions
- What does Nuclear Decay cover in WJEC A-Level Physics?
- 6 subtopics: radioactive decay, activity and half-life, distinguishing the radiations, and background radiation, randomness and spontaneity in radioactive decay, writing and balancing nuclear decay equations, the decay constant and activity and the exponential decay law in calculations. Each one has its own page with questions and model answers.
- How is Nuclear Decay organised?
- By the WJEC 1420QS specification, subtopic by subtopic, so it matches the order you are taught it in.
Every question in Nuclear Decay, 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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