Classification of Particles

Hadrons

Hadrons (e.g. protons and neutrons) are particles that feel the strong nuclear force. Hadrons are made of quarks and can be split into two categories: baryons or mesons.

Baryons

Baryons are hadrons that contain three quarks.
Protons and neutrons are both baryons.
- There are other types of baryons which can be found in cosmic rays, but you don't need to know about these at A Level.
The proton is the only stable baryon.
- All other baryons will eventually decay into a proton.

Antibaryons

The antiparticles of baryons are called antibaryons.
- Examples include antiprotons and antineutrons.

Baryon number

Baryon number, B, describes the number of baryons present.
- Each baryon has a baryon number B = 1.
- Antibaryons have a baryon number B = -1.
B is a quantum number.
- This means that it can only be an integer (i.e. you can't have B = 0.5).
B must always be conserved.
- Like energy and momentum, baryon number must be conserved in all interactions.

Mesons

Mesons are hadrons that contain a quark and an anti-quark.
Examples include pions and kaons.
- There are also many other types of mesons, but you don't need to know about them at A Level.
Mesons can be found in cosmic rays or particle accelerators.
Mesons have a baryon number B = 0 because they're not baryons!

Pions vs kaons

Pions are the exchange particle of the strong nuclear force between nucleons.
- There are three versions, each with a different electric charge: π⁺, π⁰ and π^-.
Kaons are more massive and often decay into pions. They come in many types including K⁺, K⁰ and K^-.

Leptons

Leptons are fundamental particles and so they are not made of any smaller particles. Leptons do NOT feel the strong nuclear force.

Electrons and muons

The most common type of lepton is the electron, e^-.
There are other types of leptons, such as the muon, μ^-:
- Muons are negatively charged and heavier than electrons.
- Muons are unstable and always decay into electrons.
- Muons are normally found in cosmic rays.

Neutrinos

Neutrinos are also leptons.
- Electrons and muons each have their own neutrino: the electron neutrino, ν_e, and the muon neutrino, ν_μ.
Neutrinos are (almost) massless particles with zero charge, so they don't do much.
- Just as well, because there are 100 trillion neutrinos passing through your body every second from cosmic rays!

Lepton numbers

The lepton number describes the number of leptons.
You get a different lepton number for each type of lepton.
- Electron lepton number, L_e, is 1 for electrons and electron neutrinos.
- Muon lepton number, L_μ, is 1 for muons and muon neutrinos.
Lepton numbers are quantum numbers, meaning they only come in integer numbers.
Each lepton number must be conserved individually.
Antileptons also exist. These have opposite charges and lepton numbers.

Strangeness

Strangeness is a fundamental property of matter, like mass, charge or baryon number.

Quantum number

Strangeness is a quantum number so can only take integer values.
The strange quark, s, has a strangeness of -1.
The antistrange quark, s, has a strangeness of +1.
Particles made from strange quarks (such as kaons) have an associated strangeness.

Conserved in the strong interaction

Unlike other quantum numbers, strangeness is only conserved in the strong interaction.
Strange particles, such as kaons, are produced via the strong interaction but decay via the weak interaction.
- This is why kaons are always produced in pairs (K⁺ and K^-).
- The strangeness of each particle (-1 and +1) cancel out.
In weak interactions, such as kaon decay, strangeness can change by -1, 0 or +1.

1Space, Time & Motion

1.1Motion

1.1.1Motion Basics

1.1.2Graphs of Motion

1.1.3Uniform Acceleration Equations

1.1.4Projectile Motion

1.1.5Bouncing Ball Example

1.2Forces

1.2.1Friction

1.2.2Terminal Speed

1.2.3Newton's Laws

1.2.4Exam-Style Question - Forces

1.2.5End of Topic Test - Newton's Third Law

1.3Momentum & Impulse

1.3.1Momentum

1.3.2Momentum 2

1.3.3End of Topic Test - Newton's Laws & Momentum

1.4Work, Energy & Power

1.4.1Work & Energy

1.4.2Conservation of Energy

1.4.3Power & Efficiency

1.4.4IB Multiple Choice- Work, Energy & Power

2The Particulate Nature of Matter

2.1Thermal Concepts

2.1.1Molecular Kinetic Theory Model

2.1.2Molecular Kinetic Theory Model 2

2.1.3Thermal Energy Transfer

2.1.4Thermal Energy Transfer Experiments

2.1.5Thermal Equilibrium

2.1.6Thermal Conductivity

2.1.7Heat Energy Transfer

2.2Modelling a Gas

2.2.1Ideal Gases

2.2.2Ideal Gases 2

2.2.3End of Topic Test - Thermal Energy & Ideal Gases

2.2.4Exam-Style Question - Ideal Gases

3Wave Behaviour

3.1Oscillations

3.1.1Progressive Waves

3.1.2Simple Harmonic Motion

3.2Travelling Waves

3.2.1Wave Speed & Phase Difference

3.2.2Longitudinal & Transverse Waves

3.2.3Electromagnetic Waves

3.2.4Electromagnetic Waves 2

3.2.5Sound Waves

3.3Wave Characteristics

3.3.1Polarisation

3.4Wave Behaviour

3.4.1Reflection & Absorption

3.4.2Reflection of Light

3.4.3Refraction

3.4.4Refractive index

3.5Standing Waves

3.5.1Standing Waves

3.5.2Standing Waves 2

3.5.3End of Topic Test - Standing Waves

3.5.4IB Multiple Choice - Waves

3.6Simple Harmonic Motion

3.6.1Simple Harmonic Motion

3.6.2Simple Harmonic Systems

3.6.3Energy in Simple Harmonic Motion

3.6.4End of Topic Test - Simple Harmonic Motion

3.6.5End of Topic Test - Simple Harmonic Motion

3.7Single Slit Diffraction

3.7.1Diffraction

3.8Interference

3.8.1Interference

3.8.2Interference 2

3.8.3Diffraction Gratings

3.8.4End of Topic Test - Diffraction

3.9Doppler Effect

3.9.1Doppler Effect

4Fields

4.1Circular Motion

4.1.1Circular Motion

4.1.2Centripetal Force

4.1.3IB Multiple Choice - Circular Motion

4.2Newton's Law of Gravitation

4.2.1Newton's Law

4.2.2Orbits of Planets & Satellites

4.2.3Escape Velocity & Synchronous Orbits

4.2.4End of Topic Test - Gravitational Fields

4.3Fields

4.3.1Fields

4.3.2Gravitational Field Strength

4.3.3Gravitational Potential

4.3.4Electric Field Strength

4.3.5Electrostatic & Gravitational Forces

4.3.6Electric Potential

4.3.7IB Multiple Choice - Gravitational Fields

4.4Fields at Work

4.4.1Radial Field Strength

4.4.2Orbits of Planets & Satellites

4.4.3Escape Velocity & Synchronous Orbits

4.4.4End of Topic Test - Gravitational Fields

4.4.5Uniform Electric Fields

4.4.6IB Multiple Choice - Electric Field & Potential

4.5Electric Fields

4.5.1Electric Charge

4.5.2Conservation of Charge

4.5.3Coulomb's Law

4.5.4Current

4.5.5Potential Difference

4.5.6IB Multiple Choice - Electric Charge

4.6Magnetic Effect of Electric Currents

4.6.1Magnetism

4.6.2Magnetic Field

4.6.3Magnetic Force

4.6.4Moving Charges in a Magnetic Field

4.6.5IB Multiple Choice - Magnetism

4.7Heating Effect of Currents

4.7.1Circuits

4.7.2Resistance

4.7.3Power and Conservation

4.7.4IB Multiple Choice - DC Circuits

4.8Electromagnetic Induction

4.8.1Electromagnetic Induction

4.8.2Electromagnetic Induction 2

4.8.3Magnetic Flux & Flux Linkage

4.8.4End of Topic Test - Electromagnetic Induction

4.9Power Generation & Transmission

4.9.1Alternating Currents

4.9.2Operation of a Transformer

4.10Capacitance

4.10.1Capacitance

4.10.2Parallel Plate Capacitor

4.10.3Energy Stored by a Capacitor

4.10.4Capacitor Discharge

4.10.5Capacitor Charge

4.10.6Magnetic Flux Density

4.10.7End of Topic Test - Capacitance & Flux Density

5Nuclear & Quantum Physics

5.1Discrete Energy & Radioactivity

5.1.1Atomic Spectra

5.1.2Atomic Structure

5.1.3Photons

5.1.4Discrete Energy Levels

5.1.5Alpha, Beta & Gamma Radiation

5.1.6Scientific Practices - Unstable Nuclei

5.1.7Radioactive Decay

5.1.8IB Multiple Choice - Atomic Physics

5.2Nuclear Reactions

5.2.1Mass & Energy

5.2.2Nuclear Fission

5.3The Interaction of Matter with Radiation

5.3.1Particles, Antiparticles & Photons

5.3.2Particle Interactions

5.3.3Classification of Particles

5.3.4Wave-Particle Duality

5.3.5Wave Functions & Probability

5.3.6IB Multiple Choice - Quantum Physics

5.4Nuclear Physics

5.4.1Nuclear Instability & Radioactive Decay

5.4.2Nuclear Radius

5.4.3IB Multiple Choice - Nuclear Physics

6Measurements

6.1Measurements & Errors

6.1.1Fundamental Units

6.1.2SI Prefixes, Standard Form & Converting Units

6.1.3End of Topic Test - Units & Prefixes

6.2Uncertainties & Errors

6.2.1Limitation of Physical Measurements

6.2.2Uncertainty

6.2.3Estimation

6.2.4End of Topic Test - Measurements & Errors

6.3Vectors & Scalars

6.3.1Scalars & Vectors

6.3.2Vector Problems

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