Particles and Quantum Physics

Year 1 / ASYear 2 / A-Level All Boards (AQA, Edexcel, OCR, WJEC, CCEA) AQA

A-Level Physics revision: Particles and Quantum Physics. Learning objectives, key points, worked examples and practice questions across AQA, Edexcel, OCR, WJEC and CCEA.

Exam Board:

📌 Key Points

Key Fact: Quarks (u,d,s,c,b,t) in baryons (3) and mesons (q q̄); Leptons (e,μ,τ,νₑ,ν_μ,ν_τ)

Key Fact: Interactions: strong (gluons, q-q), weak (W+/-, Z⁰, β decay), EM (γ, charged), gravity (negligible)

Key Fact: Conservation: charge, B, L, S in strong/EM; only charge, B-L in weak

Key Fact: Photoelectric: hf = φ + KE_max; threshold f₀ = φ/h; no time lag; intensity ∝ number of photons

Key Fact: de Broglie: λ = h/p = h/sqrt(2meV) for electrons; diffraction proves wave nature

Key Fact: Line spectra: electrons move between discrete levels; emission (excited->ground), absorption (ground->excited)

Key Fact: Energy levels: E_n = -13.6/n^2 eV (hydrogen); transitions give DeltaE = hf

Key Fact: Detectors: ionisation trails in cloud/bubble chambers; Si detectors measure energy

🎯 Learning Objectives

Describe the standard model: quarks, leptons, gauge bosons
Understand particle interactions: strong, weak, electromagnetic, gravitational
Apply conservation laws: charge, baryon number, lepton number, strangeness
Use the photon model: E = hf = hc/λ, momentum p = h/λ
Explain the photoelectric effect and Einstein's equation
Understand wave-particle duality: de Broglie wavelength λ = h/p
Describe atomic line spectra and energy levels
Understand particle detectors: cloud chamber, bubble chamber, semiconductor detectors

💡 Worked Example

Exam-Style Question

Question: Electrons accelerated through 150 V. Find de Broglie wavelength and explain if diffraction observable

Model Answer:

λ = h/sqrt(2meV) = 6.63x10⁻^3⁴ / sqrt(2x9.11x10⁻^3¹x1.6x10⁻¹⁹x150) ≈ 1.0x10⁻¹⁰ m = 0.1 nm. Comparable to atomic spacing -> diffraction observable (e.g. Davisson-Germer)

❓ Practice Questions

Questions:

Energy of photon with λ = 400 nm
In β⁻ decay: n -> p + e⁻ + ν̄ₑ. Check conservation laws
Find de Broglie λ for electron at 100 eV
Explain why photoelectric effect supports photon model over wave model
Hydrogen transition n=3->2. Find λ and colour

🎬 Video Resources

Particles and Quantum Physics - Overview -- YouTube Search
Particles and Quantum Physics - Exam Questions -- YouTube Search

📄 Past Papers & Exam Resources

🔗 Further Reading & Resources

Physics & Maths Tutor - Particles and Quantum Physics -- Free notes, worksheets, and past paper questions by topic
Dr Frost Maths - Particles and Quantum Physics -- Free resources, slides, and interactive questions
BBC Bitesize - Particles and Quantum Physics -- BBC Bitesize revision resources

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