Cambridge International A Level Physics (9702)

Comprehensive Exam Study Notes - A Level Content

12. Motion in a Circle

• Kinematics: Define radian and angular displacement. Use angular speed ω = 2π/T and v = rω.
• Centripetal Acceleration: Understand it is caused by a constant magnitude force always perpendicular to velocity. Use a = rω² and a = v²/r.
• Centripetal Force: Calculate using F = mrω² and F = mv²/r.

13. Gravitational Fields

• Gravitational Force: A field of force defined as force per unit mass. Outside a uniform sphere, treat mass as a point mass at its center.
• Newton's Law: Use F = Gm₁m₂/r².
• Orbits: Analyze circular orbits by equating gravitational force to centripetal force. Know the properties of geostationary orbits (24h period, west to east, directly above Equator).
• Field Strength & Potential: Derive and use g = GM/r². Define potential (work done per unit mass from infinity) and use ϕ = -GM/r and Ep = -GMm/r.

14. Temperature

• Thermal Equilibrium: Net energy transfer is zero between regions of equal temperature.
• Scales: Temperature measurement relies on physical properties (e.g., resistance, volume). Convert between Celsius and Kelvin (T/K = θ/°C + 273.15). Absolute zero is 0 K.
• Heat & State Change: Define and calculate specific heat capacity and specific latent heat (fusion/vaporization).

15. Ideal Gases

• The Mole: Amount of substance containing Avogadro's constant (NA) of particles.
• Equation of State: An ideal gas obeys pV ∝ T. Use pV = nRT and pV = NkT (where k = R/NA).
• Kinetic Theory: State basic assumptions. Understand how molecular movement causes pressure and use pV = 1/3 Nm<c²>. Compare with pV = NkT to show average translational kinetic energy Ek = 3/2 kT.

16. Thermodynamics

• Internal Energy: The sum of a random distribution of kinetic and potential energies of molecules within a system.
• First Law: Use ΔU = q + W (increase in internal energy = heat added to system + work done on system).
• Work Done: Calculate W = pΔV for gases changing volume at constant pressure.

17. Oscillations

• Simple Harmonic Motion (SHM): Acceleration is proportional to displacement and directed towards the fixed point (a = -ω²x).
• Equations: Use x = x₀ sin ωt, v = v₀ cos ωt, and v = ±ω√(x₀² - x²).
• Energy: Understand interchange between kinetic and potential energy. Total energy E = 1/2 mω²x₀².
• Damping & Resonance: Understand light, critical, and heavy damping. Resonance occurs when driving frequency equals natural frequency, causing a maximum amplitude of oscillations.

18. Electric Fields

• Uniform Fields: Calculate field strength E = ΔV/Δd between parallel plates. Describe particle motion in uniform fields.
• Point Charges: Treat charge on a sphere as a point charge at its center. Use Coulomb's law F = Q₁Q₂/(4πε₀r²).
• Field & Potential: Use E = Q/(4πε₀r²), V = Q/(4πε₀r), and Ep = Qq/(4πε₀r). Electric field is the negative of potential gradient.

19. Capacitance

• Capacitors: Define capacitance (C = Q/V) for isolated spheres and parallel plates.
• Combinations: Derive and use formulas for series (1/C = 1/C₁ + ...) and parallel (C = C₁ + ...) circuits.
• Energy & Discharge: Energy W = 1/2 QV = 1/2 CV². Analyze exponential discharge graphs, use time constant τ = RC, and equation x = x₀e^(-t/RC).

20. Magnetic Fields

• Force on Conductor/Charge: Use F = BIL sin θ (Fleming's left-hand rule) and F = BQv sin θ.
• Hall Effect: Derive and use Hall voltage VH = BI/(ntq) for finding magnetic flux density.
• Fields from Currents: Sketch patterns for straight wires, coils, solenoids. Explain forces between current-carrying conductors.
• Electromagnetic Induction: Define magnetic flux Φ = BA and flux linkage. State and use Faraday's and Lenz's laws.

21. Alternating Currents

• Characteristics: Use x = x₀ sin ωt for sinusoidal a.c. Understand that mean power is half maximum power. Use r.m.s values: I_rms = I₀/√2, V_rms = V₀/√2.
• Rectification & Smoothing: Distinguish half-wave (single diode) and full-wave (bridge rectifier). Analyze smoothing effect using a single capacitor.

22. Quantum Physics

• Photons: Electromagnetic radiation has a particulate nature. Energy E = hf. Momentum p = E/c. Use electronvolts (eV).
• Photoelectric Effect: Define threshold frequency/wavelength and work function. Use Einstein's equation hf = Φ + 1/2 mv_max².
• Wave-Particle Duality: Electron diffraction proves wave nature. Use de Broglie wavelength λ = h/p.
• Energy Levels: Atoms have discrete levels. Explain emission/absorption spectra and use hf = E₁ - E₂.

23. Nuclear Physics

• Mass-Energy: Use E = mc². Define mass defect and nuclear binding energy.
• Fusion & Fission: Sketch binding energy per nucleon vs. nucleon number and explain how fusion/fission release energy.
• Radioactive Decay: Fluctuations show decay is spontaneous and random. Use Activity A = λN, decay constant λ = 0.693/t_half, and exponential decay x = x₀e^(-λt).

24. Medical Physics

• Ultrasound: Piezo-electric effect generates/detects waves. Calculate acoustic impedance Z = ρc and reflection coefficient IR/I₀ = (Z₁ - Z₂)²/(Z₁ + Z₂)². Use attenuation I = I₀e^(-μx).
• X-Rays: Produced by electron bombardment. Calculate minimum wavelength. Understand contrast and attenuation. Explain computed tomography (CT) scanning in 3D.
• PET Scanning: Positron-emitting tracer interacts with electrons (annihilation), producing two gamma photons in opposite directions. Image created from arrival times.

25. Astronomy and Cosmology

• Standard Candles: Understand luminosity L and use inverse square law for radiant flux intensity F = L/(4πd²). Determine distances to galaxies.
• Stellar Radii: Use Wien's displacement law λ_max ∝ 1/T and Stefan-Boltzmann law L = 4πσr²T⁴ to estimate radius.
• Hubble's Law & Big Bang: Redshift indicates expansion (Δλ/λ ≈ v/c). Use Hubble's law v ≈ H₀d to support the Big Bang theory.