IB Physics Revision Notes — Complete Guide for SL and HL

IB Physics is one of the most challenging and rewarding subjects in the Diploma Programme. Whether you’re studying at Standard Level (SL) or Higher Level (HL), having well-organised revision notes is essential for exam success.

This complete guide covers every major topic in the IB Physics syllabus, highlights the key formulas you need to know, explains the differences between SL and HL, and shares proven exam strategies to help you achieve your target grade.

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IB Physics Syllabus Overview

The IB Physics course is divided into core topics (studied by both SL and HL) and additional HL-only content. Here’s the structure:

Topic	SL	HL
1. Measurements and Uncertainties	✅	✅
2. Mechanics	✅	✅
3. Thermal Physics	✅	✅
4. Waves	✅	✅
5. Electricity and Magnetism	✅	✅
6. Circular Motion and Gravitation	✅	✅
7. Atomic, Nuclear and Particle Physics	✅	✅
8. Energy Production	✅	✅
9. Wave Phenomena (HL only)	❌	✅
10. Fields (HL only)	❌	✅
11. Electromagnetic Induction (HL only)	❌	✅
12. Quantum and Nuclear Physics (HL only)	❌	✅

Assessment weighting:

• SL: Paper 1 (30%), Paper 2 (50%), IA (20%)
• HL: Paper 1 (20%), Paper 2 (36%), Paper 3 (24%), IA (20%)

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Topic 1: Measurements and Uncertainties

This foundational topic covers how physicists measure, record, and analyse data.

Key Concepts

• SI Units: metre (m), kilogram (kg), second (s), ampere (A), kelvin (K), mole (mol), candela (cd)
• Significant figures: Your answer should reflect the precision of your least precise measurement
• Systematic errors: Consistent bias in one direction (e.g., zero error on a scale)
• Random errors: Unpredictable fluctuations that vary between measurements

Key Formulas

• Percentage uncertainty: (absolute uncertainty ÷ measured value) × 100%
• Uncertainty in addition/subtraction: Add absolute uncertainties
• Uncertainty in multiplication/division: Add percentage uncertainties
• Uncertainty in powers: Multiply percentage uncertainty by the power

Common Mistakes

• Confusing precision with accuracy
• Forgetting to propagate uncertainties through calculations
• Not including units in every answer

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Topic 2: Mechanics

Mechanics is the largest and most important topic, forming the foundation for much of IB Physics.

Kinematics

Key equations of motion (constant acceleration):

• v = u + at
• s = ut + ½at²
• v² = u² + 2as
• s = ½(u + v)t

Where: s = displacement, u = initial velocity, v = final velocity, a = acceleration, t = time

Projectile motion: Treat horizontal and vertical components independently. Horizontal velocity is constant (no air resistance); vertical acceleration = g = 9.81 m/s².

Forces and Newton’s Laws

• Newton’s First Law: An object remains at rest or in uniform motion unless acted upon by a net external force.
• Newton’s Second Law: F = ma (net force equals mass times acceleration)
• Newton’s Third Law: For every action, there is an equal and opposite reaction (on different objects).

Free body diagrams are essential — practise drawing them for every force problem.

Work, Energy, and Power

• Work: W = Fs cos θ
• Kinetic energy: Eₖ = ½mv²
• Gravitational PE: Eₚ = mgh
• Elastic PE: Eₚ = ½kx²
• Power: P = W/t = Fv
• Efficiency: η = useful energy output ÷ total energy input

Momentum

• Momentum: p = mv
• Impulse: J = FΔt = Δp
• Conservation of momentum: Total momentum before = total momentum after (in a closed system)
• Elastic collision: Both momentum and kinetic energy are conserved
• Inelastic collision: Only momentum is conserved

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Topic 3: Thermal Physics

Temperature and Heat

• Temperature measures average kinetic energy of particles
• Internal energy = total kinetic energy + total potential energy of all particles
• Specific heat capacity: Q = mcΔT
• Specific latent heat: Q = mL (no temperature change during phase transitions)

Ideal Gas Law

PV = nRT (or PV = NkᵦT)

Where: P = pressure, V = volume, n = moles, R = 8.31 J/(mol·K), T = temperature in Kelvin, N = number of molecules, kᵦ = Boltzmann constant

Key relationships:

• Boyle’s Law: P ∝ 1/V (constant T)
• Charles’s Law: V ∝ T (constant P)
• Gay-Lussac’s Law: P ∝ T (constant V)

Molecular Kinetic Theory

• Average kinetic energy: Eₖ = (3/2)kᵦT
• Assumptions of ideal gas: point particles, no intermolecular forces, perfectly elastic collisions, random motion

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Topic 4: Waves

Wave Properties

• Transverse waves: Oscillation perpendicular to direction of energy transfer (e.g., light, water waves)
• Longitudinal waves: Oscillation parallel to direction of energy transfer (e.g., sound)
• Wave equation: v = fλ
• Period and frequency: T = 1/f
• Intensity: I ∝ A² (intensity is proportional to amplitude squared)

Wave Behaviour

• Reflection: Angle of incidence = angle of reflection
• Refraction: n₁ sin θ₁ = n₂ sin θ₂ (Snell’s Law)
• Total internal reflection: Occurs when angle of incidence > critical angle; sin θc = n₂/n₁
• Diffraction: Waves spread when passing through gaps or around obstacles. Most noticeable when gap width ≈ wavelength.
• Superposition: When waves overlap, their displacements add algebraically

Standing Waves

• Formed by superposition of two identical waves travelling in opposite directions
• Nodes: Points of zero displacement (destructive interference)
• Antinodes: Points of maximum displacement (constructive interference)
• Strings: fₙ = n × v/(2L)
• Open pipes: fₙ = n × v/(2L)
• Closed pipes: fₙ = n × v/(4L) (odd harmonics only)

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Topic 5: Electricity and Magnetism

Electric Circuits

• Current: I = ΔQ/Δt
• Voltage (EMF): Energy per unit charge; V = W/Q
• Resistance: R = V/I (Ohm’s Law)
• Resistivity: R = ρL/A
• Power: P = IV = I²R = V²/R

Series circuits: Same current through all components; voltages add up; R_total = R₁ + R₂ + …

Parallel circuits: Same voltage across all branches; currents add up; 1/R_total = 1/R₁ + 1/R₂ + …

Kirchhoff’s Laws

• Junction rule: ΣI_in = ΣI_out (conservation of charge)
• Loop rule: ΣV = 0 around any closed loop (conservation of energy)

Magnetic Fields

• Moving charges create magnetic fields
• Force on a current-carrying conductor: F = BIL sin θ
• Force on a moving charge: F = qvB sin θ
• Use the right-hand rule to determine force direction

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Topic 6: Circular Motion and Gravitation

Circular Motion

• Centripetal acceleration: a = v²/r = ω²r
• Centripetal force: F = mv²/r = mω²r
• Angular velocity: ω = 2π/T = 2πf
• Period of circular motion: T = 2πr/v

Newton’s Law of Gravitation

• F = GMm/r² (gravitational force between two masses)
• Gravitational field strength: g = GM/r²
• Orbital velocity: v = √(GM/r)
• Orbital period: T² = (4π²/GM)r³ (Kepler’s Third Law)

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Topic 7: Atomic, Nuclear and Particle Physics

Atomic Structure

• Rutherford’s experiment: Alpha particles scattered by gold foil → nucleus is small, dense, positively charged
• Bohr model: Electrons in discrete energy levels; photons emitted/absorbed during transitions
• Energy of photon: E = hf = hc/λ

Nuclear Physics

• Mass-energy equivalence: E = mc²
• Mass defect: Difference between mass of nucleons and mass of nucleus
• Binding energy: Energy needed to separate nucleus into individual nucleons
• Binding energy per nucleon: Peaks at iron-56 (most stable)

Radioactive Decay

• Alpha (α): Helium nucleus emitted; Z decreases by 2, A decreases by 4
• Beta minus (β⁻): Neutron → proton + electron + antineutrino
• Gamma (γ): High-energy photon; no change in Z or A
• Half-life: N = N₀ × (½)^(t/t½)
• Activity: A = λN = A₀e^(-λt)

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Topic 8: Energy Production

Energy Sources

• Fossil fuels: High energy density but produce greenhouse gases
• Nuclear fission: Splitting heavy nuclei; high energy output, radioactive waste
• Solar: Photovoltaic cells; renewable but intermittent
• Wind: Kinetic energy of air; P = ½ρAv³
• Hydroelectric: Gravitational PE of water
• Thermal energy transfer: Conduction, convection, radiation

Greenhouse Effect

• Solar radiation enters atmosphere (short wavelength)
• Earth re-radiates infrared (long wavelength)
• Greenhouse gases absorb and re-emit IR radiation, warming the surface
• Enhanced greenhouse effect: Increased greenhouse gas concentrations → global warming

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HL-Only Topics

Topic 9: Wave Phenomena

• Single-slit diffraction: First minimum at sin θ = λ/b
• Double-slit interference: Maxima at d sin θ = nλ
• Diffraction grating: d sin θ = nλ (sharper, brighter maxima)
• Thin film interference: Path difference depends on film thickness and refractive index
• Resolution: Rayleigh criterion: θ = 1.22λ/b
• Doppler effect: f’ = f × (v ± v_observer)/(v ∓ v_source)

Topic 10: Fields

• Electric field strength: E = F/q = kQ/r²
• Electric potential: V = kQ/r
• Gravitational potential: V_g = -GM/r
• Equipotential surfaces: Perpendicular to field lines; no work done moving along them
• Orbital mechanics: Total energy = -GMm/(2r)

Topic 11: Electromagnetic Induction

• Faraday’s Law: EMF = -NΔΦ/Δt (rate of change of magnetic flux)
• Lenz’s Law: Induced current opposes the change causing it
• Magnetic flux: Φ = BA cos θ
• AC generators: EMF = NBA ω sin(ωt)
• Transformers: V₁/V₂ = N₁/N₂ (ideal transformer)
• RMS values: V_rms = V₀/√2; I_rms = I₀/√2

Topic 12: Quantum and Nuclear Physics

• Photoelectric effect: E_photon = hf = Φ + Eₖ(max); threshold frequency f₀ = Φ/h
• de Broglie wavelength: λ = h/p = h/(mv)
• Heisenberg uncertainty principle: ΔxΔp ≥ h/(4π)
• Wave-particle duality: All matter exhibits both wave and particle properties
• Nuclear energy levels: Discrete gamma-ray energies from nuclear transitions
• Radioactive decay law: N = N₀e^(-λt); λ = ln 2/t½

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Exam Tips for IB Physics

Paper 1 (Multiple Choice)

• Eliminate wrong answers first — even if you’re not sure of the right answer, removing options improves your odds
• Watch for unit traps — ensure you convert to SI units before calculating
• Know your formulas — you have a data booklet, but being familiar with it saves time
• Don’t spend too long on one question — flag it and move on

Paper 2 (Short and Extended Response)

• Show all working — marks are awarded for method, not just the final answer
• Always include units in your final answer
• Draw clear diagrams — label axes, include units, use a ruler for straight lines
• Define key terms when asked — use precise IB definitions
• Structure extended responses with clear paragraphs and logical flow

Paper 3 (HL Only)

• Section A covers the practical/experimental skills — practise data analysis, graph interpretation, and error analysis
• Section B is your option topic — know it thoroughly as it’s a significant portion of Paper 3

General Strategies

• Practise past papers — the question styles are consistent year to year
• Use the data booklet during revision so you know where everything is
• Create formula flashcards for quick review
• Study the mark schemes — they show exactly what examiners are looking for

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Common Mistakes to Avoid

1. Not converting units — Always work in SI units (metres, kilograms, seconds)
2. Forgetting vector directions — Velocity, force, and momentum are vectors; direction matters
3. Ignoring significant figures — Match the precision of your data
4. Confusing mass and weight — Mass (kg) is scalar; weight (N) is a force
5. Misapplying formulas — Understand when each equation is valid (e.g., kinematic equations require constant acceleration)
6. Skipping free body diagrams — Always draw them for force problems
7. Not reading the question carefully — Underline command terms (state, explain, discuss, evaluate)
8. Rushing through calculations — A careless arithmetic error can cost you several marks

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SL vs HL: Key Differences

Aspect	SL	HL
Teaching hours	150	240
Core topics	Topics 1–8	Topics 1–12
Papers	Paper 1 & 2	Paper 1, 2 & 3
Depth	Conceptual understanding	Deeper mathematical treatment
Maths required	Basic algebra and graphs	Calculus-based approaches
IA weighting	20%	20%

HL students need to be comfortable with more complex mathematical derivations, additional topics (wave phenomena, fields, EM induction, quantum physics), and the experimental design skills tested in Paper 3.

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Recommended Study Schedule

3 Months Before Exams

• Complete all syllabus content and IA
• Begin reviewing earlier topics
• Start a formula summary sheet

2 Months Before

• Work through topic-by-topic past paper questions
• Identify weak areas and focus revision there
• Practise data analysis and graph interpretation

1 Month Before

• Full past papers under timed conditions
• Review mark schemes thoroughly
• Refine your data booklet familiarity

Final Week

• Light revision of key concepts and formulas
• Review common mistakes and tricky topics
• Rest well before the exam

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Frequently Asked Questions

Is IB Physics hard?

IB Physics is considered challenging but manageable with consistent study. HL Physics requires stronger mathematical skills, while SL Physics focuses more on conceptual understanding. The key is regular practice with past papers.

What grade do I need in IB Physics for university?

This depends on your course and university. Engineering and physics programmes typically require HL Physics with a 6 or 7. Medical programmes may accept SL Physics with a 6+. Always check specific university requirements.

How many formulas do I need to memorise?

You’re given a data booklet in the exam, so you don’t need to memorise every formula. However, you should be very familiar with the booklet’s layout and understand how to apply each formula. The most commonly used formulas (F=ma, v=fλ, PV=nRT, etc.) should be second nature.

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