2.1.10
Classification of Particles
Hadrons
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.
![Illustrative background for Baryons](https://image-v2.cdn.app.senecalearning.com/2020-01/77cd6888-3930-4a88-8c1a-3a9181603949/baryons-min,h_400,q_80,w_640.png)
![Illustrative background for Baryons ?? "content](https://image-v2.cdn.app.senecalearning.com/2020-01/77cd6888-3930-4a88-8c1a-3a9181603949/baryons-min,h_400,q_80,w_640.png)
Baryons
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.
![Illustrative background for Antibaryons](https://image-v2.cdn.app.senecalearning.com/2020-01/47a5cf5a-93d0-4672-afd8-b47bb1352307/anti%20baryons-min,h_400,q_80,w_640.png)
![Illustrative background for Antibaryons ?? "content](https://image-v2.cdn.app.senecalearning.com/2020-01/47a5cf5a-93d0-4672-afd8-b47bb1352307/anti%20baryons-min,h_400,q_80,w_640.png)
Antibaryons
Antibaryons
- The antiparticles of baryons are called antibaryons.
- Examples include antiprotons and antineutrons.
![Illustrative background for Baryon number](https://image-v2.cdn.app.senecalearning.com/courseImages/physics/OCR Gateway/atom arrangement,h_400,q_80,w_640.jpg)
![Illustrative background for Baryon number ?? "content](https://image-v2.cdn.app.senecalearning.com/courseImages/physics/OCR Gateway/atom arrangement,h_400,q_80,w_640.jpg)
Baryon number
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.
![Illustrative background for Mesons](https://image-v2.cdn.app.senecalearning.com/2020-01/77ad02fe-c5fa-4c62-a358-0ec8278ce6a9/pions-min,h_400,q_80,w_640.png)
![Illustrative background for Mesons ?? "content](https://image-v2.cdn.app.senecalearning.com/2020-01/77ad02fe-c5fa-4c62-a358-0ec8278ce6a9/pions-min,h_400,q_80,w_640.png)
Mesons
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!
![Illustrative background for Pions vs kaons](https://image-v2.cdn.app.senecalearning.com/2020-01/77ad02fe-c5fa-4c62-a358-0ec8278ce6a9/pions-min,h_400,q_80,w_640.png)
![Illustrative background for Pions vs kaons ?? "content](https://image-v2.cdn.app.senecalearning.com/2020-01/77ad02fe-c5fa-4c62-a358-0ec8278ce6a9/pions-min,h_400,q_80,w_640.png)
Pions vs kaons
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
Leptons are fundamental particles and so they are not made of any smaller particles. Leptons do NOT feel the strong nuclear force.
![Illustrative background for Electrons and muons](https://image-v2.cdn.app.senecalearning.com/2018-08/f0dbef77-32ab-413f-a688-d6bb0360faf2/electrons-atom-,h_400,q_80,w_640.jpg)
![Illustrative background for Electrons and muons ?? "content](https://image-v2.cdn.app.senecalearning.com/2018-08/f0dbef77-32ab-413f-a688-d6bb0360faf2/electrons-atom-,h_400,q_80,w_640.jpg)
Electrons and muons
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.
![Illustrative background for Neutrinos](https://image-v2.cdn.app.senecalearning.com/2018-04/eb293c7a-ab94-42a6-9acb-4408d412e30b/shutterstock_122147881,h_400,q_80,w_640.jpg)
![Illustrative background for Neutrinos ?? "content](https://image-v2.cdn.app.senecalearning.com/2018-04/eb293c7a-ab94-42a6-9acb-4408d412e30b/shutterstock_122147881,h_400,q_80,w_640.jpg)
Neutrinos
Neutrinos
- Neutrinos are also leptons.
- Electrons and muons each have their own neutrino: the electron neutrino, νe, and the muon neutrino, νμ.
- 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!
![Illustrative background for Lepton numbers](https://image-v2.cdn.app.senecalearning.com/2018-08/f0dbef77-32ab-413f-a688-d6bb0360faf2/electrons-atom-,h_400,q_80,w_640.jpg)
![Illustrative background for Lepton numbers ?? "content](https://image-v2.cdn.app.senecalearning.com/2018-08/f0dbef77-32ab-413f-a688-d6bb0360faf2/electrons-atom-,h_400,q_80,w_640.jpg)
Lepton numbers
Lepton numbers
- The lepton number describes the number of leptons.
- You get a different lepton number for each type of lepton.
- Electron lepton number, Le, is 1 for electrons and electron neutrinos.
- Muon lepton number, Lμ, 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
Strangeness is a fundamental property of matter, like mass, charge or baryon number.
![Illustrative background for Quantum number](https://image-v2.cdn.app.senecalearning.com/2018-09/bee3b772-a56b-48d1-82f2-260df4d0be8e/emotions-funny-face-,h_400,q_80,w_640.jpg)
![Illustrative background for Quantum number ?? "content](https://image-v2.cdn.app.senecalearning.com/2018-09/bee3b772-a56b-48d1-82f2-260df4d0be8e/emotions-funny-face-,h_400,q_80,w_640.jpg)
Quantum 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.
![Illustrative background for Conserved in the strong interaction](https://image-v2.cdn.app.senecalearning.com/courseImages/chemistry/2.3.1- Chemical properties/lightning-399853_640-min,h_400,q_80,w_640.jpg)
![Illustrative background for Conserved in the strong interaction ?? "content](https://image-v2.cdn.app.senecalearning.com/courseImages/chemistry/2.3.1- Chemical properties/lightning-399853_640-min,h_400,q_80,w_640.jpg)
Conserved in the strong interaction
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.
1Measurements & Errors
2Particles & Radiation
2.1Particles
2.1.1Atomic Model
2.1.2Specific Charge, Protons & Neutron Numbers
2.1.3End of Topic Test - Atomic Model
2.1.4Isotopes
2.1.5Stable & Unstable Nuclei
2.1.6End of Topic Test - Isotopes & Nuclei
2.1.7A-A* (AO3/4) - Stable & Unstable Nuclei
2.1.8Particles, Antiparticles & Photons
2.1.9Particle Interactions
2.1.10Classification of Particles
2.1.11End of Topic Test - Particles & Interactions
2.1.12Quarks & Antiquarks
2.1.13Application of Conservation Laws
2.1.14End of Topic Test - Leptons & Quarks
2.1.15Exam-Style Question - Radioactive Decay
2.2Electromagnetic Radiation & Quantum Phenomena
3Waves
3.1Progressive & Stationary Waves
3.2Refraction, Diffraction & Interference
4Mechanics & Materials
4.1Force, Energy & Momentum
4.1.1Scalars & Vectors
4.1.2Vector Problems
4.1.3End of Topic Test - Scalars & Vectors
4.1.4Moments
4.1.5Centre of Mass
4.1.6End of Topic Test - Moments & Centre of Mass
4.1.7Motion in a Straight Line
4.1.8Graphs of Motion
4.1.9Bouncing Ball Example
4.1.10End of Topic Test - Motion in a Straight Line
4.1.11Acceleration Due to Gravity
4.1.12Projectile Motion
4.1.13Friction
4.1.14Terminal Speed
4.1.15End of Topic Test - Acceleration Due to Gravity
4.1.16Newton's Laws
4.1.17Momentum
4.1.18Momentum 2
4.1.19End of Topic Test - Newton's Laws & Momentum
4.1.20A-A* (AO3/4) - Newton's Third Law
4.1.21Work & Energy
4.1.22Power & Efficiency
4.1.23Conservation of Energy
4.1.24End of Topic Test - Work, Energy & Power
4.1.25Exam-Style Question - Forces
5Electricity
5.1Current Electricity
5.1.1Basics of Electricity
5.1.2Current-Voltage Characteristics
5.1.3End of Topic Test - Basics of Electricity
5.1.4Resistivity
5.1.5Superconductivity
5.1.6A-A* (AO3/4) - Superconductivity
5.1.7End of Topic Test - Resistivity & Superconductors
5.1.8Circuits
5.1.9Power and Conservation
5.1.10Potential Divider
5.1.11Emf & Internal Resistance
5.1.12End of Topic Test - Power & Potential
5.1.13Exam-Style Question - Resistance
6Further Mechanics & Thermal Physics (A2 only)
6.1Periodic Motion (A2 only)
6.2Thermal Physics (A2 only)
7Fields & Their Consequences (A2 only)
7.1Fields (A2 only)
7.2Gravitational Fields (A2 only)
7.3Electric Fields (A2 only)
7.4Capacitance (A2 only)
7.5Magnetic Fields (A2 only)
7.5.1Magnetic Flux Density
7.5.2End of Topic Test - Capacitance & Flux Density
7.5.3Moving Charges in a Magnetic Field
7.5.4Magnetic Flux & Flux Linkage
7.5.5Electromagnetic Induction
7.5.6Electromagnetic Induction 2
7.5.7Alternating Currents
7.5.8Operation of a Transformer
7.5.9Magnetic Flux Density
7.5.10End of Topic Test - Electromagnetic Induction
8Nuclear Physics (A2 only)
8.1Radioactivity (A2 only)
8.1.1Rutherford Scattering
8.1.2Alpha & Beta Radiation
8.1.3Gamma Radiation
8.1.4Radioactive Decay
8.1.5Half Life
8.1.6End of Topic Test - Radioactivity
8.1.7Nuclear Instability
8.1.8Nuclear Radius
8.1.9Mass & Energy
8.1.10Binding Energy
8.1.11Induced Fission
8.1.12Safety Aspects of Nuclear Reactors
8.1.13End of Topic Test - Nuclear Physics
8.1.14A-A* (AO3/4) - Nuclear Fusion
9Option: Astrophysics (A2 only)
9.1Telescopes (A2 only)
9.2Classification of Stars (A2 only)
9.3Cosmology (A2 only)
10Option: Medical Physics (A2 only)
10.1Physics of the Eye (A2 only)
10.2Physics of the Ear (A2 only)
10.3Biological Measurement (A2 only)
10.4Non-Ionising Imaging (A2 only)
10.5X-Ray Imaging (A2 only)
10.6Radionuclide Imaging & Therapy (A2 only)
11Option: Engineering Physics (A2 only)
11.1Rotational Dynamics (A2 only)
11.2Thermodynamics & Engines (A2 only)
12Option: Turning Points in Physics (A2 only)
12.1Discovery of the Electron (A2 only)
12.2Wave-Particle Duality (A2 only)
Jump to other topics
1Measurements & Errors
2Particles & Radiation
2.1Particles
2.1.1Atomic Model
2.1.2Specific Charge, Protons & Neutron Numbers
2.1.3End of Topic Test - Atomic Model
2.1.4Isotopes
2.1.5Stable & Unstable Nuclei
2.1.6End of Topic Test - Isotopes & Nuclei
2.1.7A-A* (AO3/4) - Stable & Unstable Nuclei
2.1.8Particles, Antiparticles & Photons
2.1.9Particle Interactions
2.1.10Classification of Particles
2.1.11End of Topic Test - Particles & Interactions
2.1.12Quarks & Antiquarks
2.1.13Application of Conservation Laws
2.1.14End of Topic Test - Leptons & Quarks
2.1.15Exam-Style Question - Radioactive Decay
2.2Electromagnetic Radiation & Quantum Phenomena
3Waves
3.1Progressive & Stationary Waves
3.2Refraction, Diffraction & Interference
4Mechanics & Materials
4.1Force, Energy & Momentum
4.1.1Scalars & Vectors
4.1.2Vector Problems
4.1.3End of Topic Test - Scalars & Vectors
4.1.4Moments
4.1.5Centre of Mass
4.1.6End of Topic Test - Moments & Centre of Mass
4.1.7Motion in a Straight Line
4.1.8Graphs of Motion
4.1.9Bouncing Ball Example
4.1.10End of Topic Test - Motion in a Straight Line
4.1.11Acceleration Due to Gravity
4.1.12Projectile Motion
4.1.13Friction
4.1.14Terminal Speed
4.1.15End of Topic Test - Acceleration Due to Gravity
4.1.16Newton's Laws
4.1.17Momentum
4.1.18Momentum 2
4.1.19End of Topic Test - Newton's Laws & Momentum
4.1.20A-A* (AO3/4) - Newton's Third Law
4.1.21Work & Energy
4.1.22Power & Efficiency
4.1.23Conservation of Energy
4.1.24End of Topic Test - Work, Energy & Power
4.1.25Exam-Style Question - Forces
5Electricity
5.1Current Electricity
5.1.1Basics of Electricity
5.1.2Current-Voltage Characteristics
5.1.3End of Topic Test - Basics of Electricity
5.1.4Resistivity
5.1.5Superconductivity
5.1.6A-A* (AO3/4) - Superconductivity
5.1.7End of Topic Test - Resistivity & Superconductors
5.1.8Circuits
5.1.9Power and Conservation
5.1.10Potential Divider
5.1.11Emf & Internal Resistance
5.1.12End of Topic Test - Power & Potential
5.1.13Exam-Style Question - Resistance
6Further Mechanics & Thermal Physics (A2 only)
6.1Periodic Motion (A2 only)
6.2Thermal Physics (A2 only)
7Fields & Their Consequences (A2 only)
7.1Fields (A2 only)
7.2Gravitational Fields (A2 only)
7.3Electric Fields (A2 only)
7.4Capacitance (A2 only)
7.5Magnetic Fields (A2 only)
7.5.1Magnetic Flux Density
7.5.2End of Topic Test - Capacitance & Flux Density
7.5.3Moving Charges in a Magnetic Field
7.5.4Magnetic Flux & Flux Linkage
7.5.5Electromagnetic Induction
7.5.6Electromagnetic Induction 2
7.5.7Alternating Currents
7.5.8Operation of a Transformer
7.5.9Magnetic Flux Density
7.5.10End of Topic Test - Electromagnetic Induction
8Nuclear Physics (A2 only)
8.1Radioactivity (A2 only)
8.1.1Rutherford Scattering
8.1.2Alpha & Beta Radiation
8.1.3Gamma Radiation
8.1.4Radioactive Decay
8.1.5Half Life
8.1.6End of Topic Test - Radioactivity
8.1.7Nuclear Instability
8.1.8Nuclear Radius
8.1.9Mass & Energy
8.1.10Binding Energy
8.1.11Induced Fission
8.1.12Safety Aspects of Nuclear Reactors
8.1.13End of Topic Test - Nuclear Physics
8.1.14A-A* (AO3/4) - Nuclear Fusion
9Option: Astrophysics (A2 only)
9.1Telescopes (A2 only)
9.2Classification of Stars (A2 only)
9.3Cosmology (A2 only)
10Option: Medical Physics (A2 only)
10.1Physics of the Eye (A2 only)
10.2Physics of the Ear (A2 only)
10.3Biological Measurement (A2 only)
10.4Non-Ionising Imaging (A2 only)
10.5X-Ray Imaging (A2 only)
10.6Radionuclide Imaging & Therapy (A2 only)
11Option: Engineering Physics (A2 only)
11.1Rotational Dynamics (A2 only)
11.2Thermodynamics & Engines (A2 only)
12Option: Turning Points in Physics (A2 only)
12.1Discovery of the Electron (A2 only)
12.2Wave-Particle Duality (A2 only)
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