AQA A Level Physics –
Particles & Particle
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, What are some examples of strange particles? Kaons
What are strange particles? Subatomic particles that have a non-zero value for strangeness.
What makes a strange particle different from other It has a strange quark
particles? It has a longer half life than expected
It decays by weak interaction
Why do strange particles have a very long lifetime? Although strange particles interact through the strong nuclear force, the strange
quark itself can decay only by conversion to a quark of a different type (such as u or
d) through the weak interaction.
It was discovered that in weak interactions strangeness was not conserved!
This is why it has a longer half life than expected.
What does the strange quark (and antiquark) decay into? A quark, an electron and an electron antineutrino.
Why are strange particles produced in pairs? Strangeness before must be equal to strangeness after.
Suggests that they have an additive conserved quality.
Is strangeness conserved in strong interactions? Yes. But not in weak interactions.
What are the 4 conservation laws? Charge (Q)
Baryon number (B)
Lepton number (electron & muon) (L)
Strangeness (S)
𝑛 → 𝑒+ + 𝑒− No.
Is this possible? The baryon number is not conserved.
1→0+0
Has to be equal on both sides so it's not possible.
Give two examples of baryons Neutrons
Protons
Give two examples of mesons Pions
Kaons
What are the 2 sub-groups of hadrons? Baryons and mesons
Particles & Particle
Physics 2026 | Study
Guide, Practice Questions,
Answers, Rationales &
Exam Review | Complete
Ethics Study Guide
Updated 2026 Questions and Answers
100% Verified Exam Prep and Comprehensive
Rationales
Included
, What are some examples of strange particles? Kaons
What are strange particles? Subatomic particles that have a non-zero value for strangeness.
What makes a strange particle different from other It has a strange quark
particles? It has a longer half life than expected
It decays by weak interaction
Why do strange particles have a very long lifetime? Although strange particles interact through the strong nuclear force, the strange
quark itself can decay only by conversion to a quark of a different type (such as u or
d) through the weak interaction.
It was discovered that in weak interactions strangeness was not conserved!
This is why it has a longer half life than expected.
What does the strange quark (and antiquark) decay into? A quark, an electron and an electron antineutrino.
Why are strange particles produced in pairs? Strangeness before must be equal to strangeness after.
Suggests that they have an additive conserved quality.
Is strangeness conserved in strong interactions? Yes. But not in weak interactions.
What are the 4 conservation laws? Charge (Q)
Baryon number (B)
Lepton number (electron & muon) (L)
Strangeness (S)
𝑛 → 𝑒+ + 𝑒− No.
Is this possible? The baryon number is not conserved.
1→0+0
Has to be equal on both sides so it's not possible.
Give two examples of baryons Neutrons
Protons
Give two examples of mesons Pions
Kaons
What are the 2 sub-groups of hadrons? Baryons and mesons
