Ten lessons covering measurements, particles, waves, mechanics, electricity, fields, thermal physics, oscillations and nuclear physics for A-level, with exam skills and interactive explorers.
A study guide to A-level Physics, not a full course or textbook. The paper structure follows the AQA 7408 page; other boards (Edexcel, OCR, WJEC) organize topics differently. Physics content is standard A-level knowledge for study, and you should check your own specification and data booklet. Lab numbers are practice values.
['GCSE Physics or Combined Science at higher tier', 'A-level Mathematics alongside']
Course outline
Measurements, errors and units
Use SI units, uncertainties and graphs.
Particles and radiation
Describe atomic structure, the standard model and radioactive decay.
Waves and optics
Describe wave properties, interference and diffraction.
Mechanics and materials
Apply motion, forces, energy and momentum with material properties.
Electricity and circuits
Use Ohm's law, resistivity, internal resistance and series and parallel circuits.
Fields, gravitation and electric fields
Compare gravitational and electric fields and use Newton's and Coulomb's laws.
Thermal physics and gases
Use specific heat, gas laws and kinetic theory.
Circular motion and oscillations
Analyze circular motion and simple harmonic motion.
Magnetic fields and electromagnetic induction
Use forces on currents and charges and Faraday's and Lenz's laws.
Nuclear energy, astrophysics and the exam
Link binding energy to energy release and plan for the AQA papers.
Sources and curriculum note
Reviewed October 7, 2026. Confirm the specification for your board and exam year.
Read every lesson below. The interactive reader above contains the same explanations, with visual tools and quizzes.
1. Measurements, errors and units
Learning goal: Use SI units, uncertainties and graphs.
Physics uses SI base units: meter, kilogram, second, ampere, kelvin and mole. Derived units such as the newton are combinations of these. Check an equation with homogeneity: both sides must have the same units. Prefixes such as milli, micro and nano scale quantities by powers of ten.
Every measurement has uncertainty. Percentage uncertainty = absolute uncertainty / value x 100. When adding or subtracting, add absolute uncertainties. When multiplying or dividing, add percentage uncertainties, and for a power, multiply the percentage uncertainty by the power. Random errors scatter results and repeated readings reduce them; systematic errors shift all readings the same way, for example a zero error.
Vectors have magnitude and direction. Resolve a vector at angle theta into components V cos theta and V sin theta. Add vectors by components or by a scale diagram. Scalars such as mass and energy have no direction.
On a graph, gradients and intercepts carry meaning. Draw a line of best fit, choose a large triangle to find the gradient, and use worst-fit lines to estimate the uncertainty in the gradient.
Worked example
Find uncertainty.
Percent uncertainty of each
Add
Convert to absolute
State result
Practice problem and solution
A length is 50 cm with absolute uncertainty 1 cm. What is the percentage uncertainty? Enter a number.
1 / 50 x 100 = 2.
Mental model: Use SI units, combine uncertainties by the rules and read graphs carefully.
Common trap: Adding percentage uncertainties for a sum.
2. Particles and radiation
Learning goal: Describe atomic structure, the standard model and radioactive decay.
An atom has a nucleus of protons and neutrons with electrons around it. Nucleon number A is protons plus neutrons and proton number Z is the number of protons. Isotopes have the same Z and different A. The strong nuclear force holds nucleons together over very short ranges.
Radioactive decay is random. Alpha decay emits a helium nucleus, beta minus decay turns a neutron into a proton and emits an electron and an antineutrino, and gamma emission releases a photon. The activity A = lambda N, and the number of nuclei follows N = N0 e^(-lambda t). The half-life is ln 2 / lambda.
The standard model includes quarks (up, down, strange and others) and leptons (electron, neutrino). Protons are uud and neutrons are udd. Hadrons are made of quarks, and baryons contain three. Every particle has an antiparticle with the same mass and opposite charge. Conservation of charge, baryon number and lepton number applies in interactions.
Light behaves as photons with energy E = hf = hc / wavelength. In the photoelectric effect, electrons are emitted only if the photon energy exceeds the work function, which supports the particle picture. Electrons also show wave behavior with de Broglie wavelength h / (mv).
Worked example
Use conservation.
Charge
Baryon number
Lepton number
Check both sides
Practice problem and solution
A sample starts with 800 nuclei and has a half-life of 3 hours. How many remain after 9 hours? Enter a number.
9 hours is 3 half-lives, 800 / 8 = 100.
Mental model: Decay is random and exponential; conservation laws govern interactions; photons carry hf.
Common trap: Thinking half-life means the sample is gone after two half-lives.
3. Waves and optics
Learning goal: Describe wave properties, interference and diffraction.
A wave transfers energy without transferring matter. Wave speed c = f x wavelength. Transverse waves oscillate at right angles to the direction of travel and can be polarized, and longitudinal waves oscillate along it. Phase difference tells how far apart in the cycle two points are.
Superposition adds displacements. Constructive interference needs a path difference of a whole number of wavelengths, and destructive needs an odd number of half wavelengths. Stationary waves form from two waves of the same frequency traveling in opposite directions and have nodes and antinodes. A string of length L fixed at both ends has a fundamental frequency f = v / 2L.
A diffraction grating gives maxima at d sin theta = n x wavelength, where d is the line spacing. Young's double slit gives fringe spacing w = wavelength x D / s, with D the slit-to-screen distance and s the slit separation. Single-slit diffraction gives a central maximum wider with a narrower slit.
Refraction obeys n1 sin theta1 = n2 sin theta2. Total internal reflection occurs beyond the critical angle, with sin C = n2 / n1 for n1 greater than n2. Optical fibers use this to carry light.
Worked example
Find a wavelength.
Measure fringe spacing
Measure D and s
Rearrange
Calculate
Practice problem and solution
Light of wavelength 600 nm passes through slits 0.3 mm apart onto a screen 1.5 m away. What is the fringe spacing in mm? Enter a number.
(600e-9 x 1.5) / 0.3e-3 = 3e-3 m = 3 mm.
Mental model: Interference depends on path difference; slits and gratings give measurable patterns.
Common trap: Mixing nanometers and meters.
4. Mechanics and materials
Learning goal: Apply motion, forces, energy and momentum with material properties.
For constant acceleration use v = u + at, s = ut + 1/2 at^2 and v^2 = u^2 + 2as. Projectiles have constant horizontal velocity and vertical acceleration g. Newton's second law is F = ma, or more generally force is the rate of change of momentum. Conservation of momentum applies in collisions where no external force acts.
Work done = F s cos theta. Kinetic energy is 1/2 m v^2 and gravitational potential energy is m g h. Power is energy transferred per second. Efficiency is useful output divided by total input. Moments are force times perpendicular distance, and equilibrium needs zero resultant force and zero resultant moment.
In materials, stress = force / area and strain = extension / original length. The Young modulus is stress / strain. Hooke's law says force is proportional to extension up to the limit of proportionality. The area under a force-extension graph gives energy stored, 1/2 F x for a linear region. Viscosity and drag also appear in fluid motion.
Always draw a free-body diagram. Check whether a quantity is a vector, and give directions with signs.
Worked example
Solve a problem.
Free-body diagram
Choose equation
Substitute with units
Check
Practice problem and solution
A 2 kg mass is raised 5 m. Using g = 9.8, what is the gain in potential energy in J? Enter a number.
2 x 9.8 x 5 = 98.
Mental model: Use suvat, conservation laws and energy; stress and strain describe materials.
Common trap: Forgetting to resolve into components.
5. Electricity and circuits
Learning goal: Use Ohm's law, resistivity, internal resistance and series and parallel circuits.
Current is the rate of flow of charge, I = Q / t. Potential difference is energy transferred per unit charge, V = W / Q. Resistance R = V / I. Ohm's law applies to ohmic conductors at constant temperature. A filament lamp is non-ohmic because resistance rises as it heats.
Resistivity rho links resistance to the material: R = rho L / A. In series, R = R1 + R2 and current is shared. In parallel, 1/R = 1/R1 + 1/R2, and voltage is the same across each branch. Power P = V I = I^2 R = V^2 / R.
A cell has internal resistance r, so terminal pV = emf - I r. A greater current gives a lower terminal voltage. Kirchhoff's laws say current is conserved at junctions and the sum of emfs equals the sum of potential drops around a loop. A potential divider gives Vout = Vin x R2 / (R1 + R2). Thermistors and light-dependent resistors make sensors.
Capacitors store charge Q = C V and energy 1/2 C V^2. Discharge through a resistor follows an exponential with time constant RC.
Worked example
Analyze a circuit.
Simplify
Find total R
Find current
Find voltages
Practice problem and solution
A 12 V cell has internal resistance 1 ohm and drives 2 A. What is the terminal voltage? Enter a number.
12 - 2 x 1 = 10.
Mental model: Series adds resistances, parallel adds reciprocals, and internal resistance lowers the terminal voltage.
Common trap: Using the series formula for parallel resistors.
6. Fields, gravitation and electric fields
Learning goal: Compare gravitational and electric fields and use Newton's and Coulomb's laws.
Newton's law of gravitation says the force between two masses is F = G m1 m2 / r^2. Gravitational field strength g = G M / r^2. Gravitational potential is -G M / r, and the potential energy of a mass is m times that. Satellites in circular orbits have v^2 = G M / r and a period T with T^2 proportional to r^3.
Coulomb's law gives the force between charges: F = Q1 Q2 / (4 pi epsilon0 r^2). Electric field strength E = F / Q, and in a uniform field between plates E = V / d. Electric potential is Q / (4 pi epsilon0 r). Field lines show direction and strength.
The two fields are similar: both follow inverse-square laws. They differ because gravity is always attractive and electric forces can attract or repel. The electric force is much stronger than gravity between charged particles.
Capacitance is charge stored per unit voltage. In a magnetic field a wire carrying current feels a force F = B I L sin theta, and a charged particle moving at right angles to B moves in a circle of radius r = m v / (B q).
Worked example
Compare forces.
Write both laws
Insert values
Compute
Compare magnitudes
Practice problem and solution
A uniform field has plates 0.02 m apart with 400 V across them. What is the field strength in V per m? Enter a number.
400 / 0.02 = 20000.
Mental model: Inverse-square laws govern both fields; gravity attracts only; E = V / d between plates.
Common trap: Using the plate spacing in the wrong units.
7. Thermal physics and gases
Learning goal: Use specific heat, gas laws and kinetic theory.
Specific heat capacity c is the energy needed to raise 1 kg by 1 K: Q = m c delta T. Specific latent heat is the energy to change state per kg at constant temperature. Internal energy is the sum of kinetic and potential energies of the particles.
The ideal gas equation is pV = nRT or pV = N k T, where k is the Boltzmann constant 1.38 x 10^-23 J per K. Temperature must be in kelvin: T = theta + 273. Boyle's law says pV is constant at fixed temperature, and pressure is proportional to temperature at fixed volume.
Kinetic theory links pressure to molecular motion: pV = 1/3 N m (c rms)^2. The mean kinetic energy of a molecule is 3/2 k T, so absolute temperature measures average kinetic energy. Real gases deviate from ideal behavior at high pressure and low temperature.
Convert units before calculating: liters to cubic meters, kilopascals to pascals, and Celsius to kelvin.
Worked example
Use the gas law.
Convert units
Choose form
Substitute
Check
Practice problem and solution
A gas has volume 2 m3 at 100 kPa. At the same temperature it is compressed to 1 m3. What is the pressure in kPa? Enter a number.
pV is constant: 100 x 2 = p x 1, so p = 200.
Mental model: Use kelvin; pV = nRT; mean kinetic energy is proportional to absolute temperature.
Common trap: Using Celsius in gas law calculations.
8. Circular motion and oscillations
Learning goal: Analyze circular motion and simple harmonic motion.
An angle in radians is arc length divided by radius. Angular speed omega = 2 pi f = 2 pi / T, and v = omega r. The centripetal acceleration is v^2 / r = omega^2 r toward the center, and the resultant force is m v^2 / r. The force does no work because it is perpendicular to motion.
Simple harmonic motion has acceleration proportional to displacement and directed to the equilibrium: a = -omega^2 x. Displacement x = A cos (omega t), and the maximum speed is omega A. For a mass on a spring the period T = 2 pi times the square root of m / k, and for a pendulum T = 2 pi times the square root of L / g.
Energy swaps between kinetic and potential, with total energy 1/2 m omega^2 A^2. Damping removes energy and reduces amplitude. Forced oscillations at the natural frequency give resonance with a large amplitude. Light damping gives a sharp peak, and heavy damping flattens it.
Resonance can be useful in musical instruments and harmful in bridges. Sketch graphs of displacement, velocity and acceleration against time and note the phase shifts.
Worked example
Describe SHM.
Equation
Graph
Energy
Period
Practice problem and solution
A pendulum is 1 m long. Using g = 9.8, what is the period in seconds to one decimal place? Enter a number.
2 pi sqrt(1/9.8) = 2.007, about 2.0.
Mental model: SHM has acceleration proportional to displacement toward the center; resonance needs matching frequencies.
Common trap: Using degrees in SHM equations.
9. Magnetic fields and electromagnetic induction
Learning goal: Use forces on currents and charges and Faraday's and Lenz's laws.
A wire of length L carrying current I at angle theta to a magnetic field B feels a force F = B I L sin theta. Fleming's left-hand rule gives its direction. A charge q moving at speed v at right angles to the field feels F = B q v, which acts as the centripetal force, so the path is a circle of radius r = m v / (B q).
Magnetic flux is Phi = B A cos theta, and flux linkage is N Phi for a coil of N turns. Faraday's law says the induced emf equals the rate of change of flux linkage: emf = N delta Phi / delta t. Lenz's law says the induced current opposes the change that produces it, which follows from conservation of energy, and gives the minus sign in the law.
A generator rotates a coil in a field to produce an alternating emf. A transformer changes alternating voltage: Vs / Vp = Ns / Np, and an ideal transformer conserves power. Real transformers lose energy through resistance of the windings, eddy currents and flux leakage, which a laminated iron core reduces.
Check directions with the rules, and be clear whether a question asks for a force on a wire, a moving charge or an induced emf.
Worked example
Find an emf.
Find flux change
Find the time
Multiply by turns
State direction
Practice problem and solution
A transformer has 100 primary turns and 500 secondary turns, with 12 V on the primary. What is the secondary voltage in V? Enter a number.
12 x 500 / 100 = 60.
Mental model: Magnetic force depends on B, I or v and angle; induced emf is the rate of change of flux linkage.
Common trap: Forgetting the angle in the force or flux formula.
10. Nuclear energy, astrophysics and the exam
Learning goal: Link binding energy to energy release and plan for the AQA papers.
The mass of a nucleus is less than the sum of its nucleons. The difference, the mass defect, corresponds to the binding energy through E = m c^2 with c = 3.00 x 10^8 m per s. Binding energy per nucleon peaks near iron, so fusing light nuclei or splitting heavy ones releases energy. Fission in reactors uses chain reactions controlled by moderators and control rods.
Stars form from clouds of gas and fuse hydrogen to helium, balancing gravity and radiation pressure. Luminosity, the power radiated, follows the Stefan-Boltzmann law L = 4 pi r^2 sigma T^4. Wien's law gives the peak wavelength inversely proportional to temperature. The Hertzsprung-Russell diagram plots luminosity against temperature.
AQA A-level Physics (7408) has three 2-hour papers. Papers 1 and 2 are each 85 marks (34 percent) with 60 marks of written questions and 25 multiple-choice questions. Paper 3 is 80 marks (32 percent) and has a compulsory section on practical skills and data analysis with 45 marks, and an optional topic worth 35 marks, chosen from sections 9 to 13 of the specification. Check the AQA specification for the option titles offered by your school.
Allow about a minute per mark and show full working. For practical questions, identify variables, uncertainties and a method for improving accuracy. Check the AQA page for the current format.
Worked example
Plan the exam.
Read the paper
Marks per minute
Easy first
Check units
Practice problem and solution
A mass defect of 1.0 x 10^-30 kg corresponds to what energy in units of 10^-14 J (c = 3.0 x 10^8)? Enter a number.
1e-30 x 9e16 = 9e-14 J.
Mental model: Binding energy per nucleon explains fission and fusion; know the three papers and the options.