Key term
CCEA A-Level Physics 1210
Physical Quantities, Scalars and Vectors
Moments and Equilibrium
Linear Motion and Dynamics
Newton's Laws of Motion
Linear Momentum and Impulse
Work, Energy and Power
Current, Charge and Potential Difference
Resistance and Resistivity
Topic overviewResistance and Ohm's lawOhmic and non-ohmic behaviourResistors in series and in parallelInvestigating current, voltage and resistance in series and parallel circuitsElectrical power and energy in resistive circuitsResistivity and the equation R = ρl/AMeasuring the resistivity of a metalCurrent–voltage characteristics of a conductor, a lamp and a diodeResistance, temperature and superconductivity
Internal Resistance and Potential Dividers
Topic overviewInternal resistance and terminal potential differenceConsequences of internal resistance for external circuitsMeasuring electromotive force and internal resistanceThe potential divider and variable outputPotential dividers in lighting and heating control circuitsLoaded potential dividers and output voltage calculations
Waves
Refraction
Lenses
Superposition, Interference and Diffraction
Topic overviewSuperposition of wavesStanding waves, nodes and antinodesStanding waves on stretched stringsStanding waves in a pipe closed at one endMeasuring the speed of sound with a resonance tubeConditions for observable interferencePath difference and phase differenceYoung's double slitDiffraction at a single slitThe diffraction grating
Quantum Physics
Wave-Particle Duality
Astronomy
Practical Skills and Data Analysis
Topic overviewChoosing and using measuring instrumentsPrecision, accuracy and recording measurementsUsing the cathode ray oscilloscope to measure voltage and frequencyTables, graphs and presenting resultsLinearising a relationship and using the gradientAbsolute and percentage uncertaintyCombining uncertainties and uncertainty on a graphRandom and systematic error, reliability and refining an experiment
Deformation of Solids
Thermal Physics
Topic overviewBoyle's law, Charles's law and the pressure lawThe ideal gas equation pV = nRTThe Avogadro constant, the mole and pV = NkTInternal energy and the distribution of molecular energyThe kinetic theory equation pV = ⅓Nm⟨c²⟩Average molecular kinetic energy and temperatureAbsolute zero and the kelvin scaleSpecific heat capacity and the electrical method
Uniform Circular Motion
Simple Harmonic Motion
Topic overviewDefining simple harmonic motion and a = −ω²xDisplacement, velocity and acceleration: x = A cos ωtThe simple pendulum and T = 2π√(l/g)The loaded spiral spring and T = 2π√(m/k)SHM graphs and finding velocity from a gradientFree vibrations, forced vibrations and resonanceDamping: light, critical and over-damping
The Nucleus and Radioactive Decay
Topic overviewAlpha-particle scattering and the nuclear atomNuclear radius and nucleon numberThe density of nuclear matterAlpha, beta and gamma radiation: nature, penetration and rangeNuclear equations and changes in nucleon and proton numberThe random and exponential nature of radioactive decayActivity, the decay constant and A = −λNExponential decay calculations with A = A₀e^(−λt)Half-life and measuring it
Nuclear Energy, Fission and Fusion
Gravitational Fields
Electric Fields
Capacitors
Magnetic Fields
Charged Particles and Accelerators
Quantum Physics
Work function, threshold frequency and Einstein's equation
- 3 things to know
- Unit AS 2
Overview
Work function of a metal, threshold frequency and einstein's photoelectric equation, defining every symbol.
What you need to know
Answer each one before you reveal it.
Your recallNot started
Key term
Why does Einstein's equation refer to the maximum kinetic energy rather than simply the kinetic energy?
Key term
Define the work function of a metal.
Questions from this subtopic
Each one with the model answer underneath.
- 1
Define the work function of a metal.
Model answer
The work function is the minimum energy needed to remove an electron from the surface of the metal, measured in joules or electronvolts.
- 2
Define the threshold frequency.
Model answer
The threshold frequency is the lowest frequency of radiation that will just release an electron from the surface of a particular metal.
- 3
State the relationship between the work function and the threshold frequency, defining each symbol.
Model answer
φ = hf₀, where φ is the work function in joules, h is the Planck constant in J s and f₀ is the threshold frequency in hertz.
- 4
State Einstein's photoelectric equation, defining every symbol.
Model answer
½mv²max = hf − hf₀, where m is the mass of an electron in kg, v max is the maximum speed of an emitted electron in m s⁻¹, h is the Planck constant in J s, f is the frequency of the incident radiation in Hz and f₀ is the threshold frequency in Hz.
- 5
Write Einstein's photoelectric equation in terms of the work function.
Model answer
hf = φ + ½mv²max, where hf is the energy delivered by one photon, φ is the work function of the metal and ½mv²max is the greatest kinetic energy any released electron can have.
- 6
Why does Einstein's equation refer to the maximum kinetic energy rather than simply the kinetic energy?
Model answer
Only electrons right at the surface escape having lost the minimum energy φ, while electrons from deeper in the metal lose more energy on the way out, so the emitted electrons have a range of energies up to that maximum.
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