amazon.co.ukWaves
A-Level Physics revision: Waves. Learning objectives, key points, worked examples and practice questions across AQA, Edexcel, OCR, WJEC and CCEA.
📌 Key Points
Key Fact: Wave eqn: v = fλ; phase difference Deltaφ = 2piDeltax/λ = 2pift
Key Fact: Superposition: y_total = y₁ + y₂; constructive: Deltaφ = 2npi; destructive: Deltaφ = (2n+1)pi
Key Fact: Standing waves: nodes (A=0) at fixed ends; antinodes (A=max) at λ/4 intervals
Key Fact: Double slit: fringe spacing w = λD/s; single slit: first minima at a sinθ = λ
Key Fact: Polarisation: only transverse waves; Malus's law I = I₀cos^2θ
Key Fact: Doppler: f' = f(v +/- v_o)/(v ∓ v_s) for sound; Deltaf/f = v/c for light (non-relativistic)
Key Fact: TIR: occurs when n₁ > n₂ and θ > θ_c = arcsin(n₂/n₁); optical fibres use TIR
Key Fact: Refractive index: n = c/v = c₁/c₂; Snell: n₁sinθ₁ = n₂sinθ₂
🎯 Learning Objectives
- Describe wave properties: amplitude, wavelength, frequency, period, phase
- Use the wave equation v = fλ
- Explain superposition, interference (constructive/destructive), standing waves
- Describe diffraction and single/double slit patterns
- Understand polarisation of transverse waves
- Apply the Doppler effect for sound and light
- Describe optical fibres: total internal reflection, critical angle
- Understand refractive index and Snell's law
💡 Worked Example
Exam-Style Question
Question: Light of wavelength 500 nm passes through double slits 0.2 mm apart. Fringes observed on screen 2.5 m away. Find fringe spacing
Model Answer:
w = λD/s = (500x10⁻⁹ x 2.5) / (0.2x10⁻^3) = 6.25x10⁻^3 m = 6.25 mm
❓ Practice Questions
Questions:
- A wave travels at 340 m/s with frequency 170 Hz. Find wavelength
- Two coherent sources 1.5 mm apart produce fringes 4 mm apart at 3 m. Find λ
- Find critical angle for glass-air interface (n_glass = 1.5)
- A police siren at 800 Hz approaches at 30 m/s. Find frequency heard (v_sound=340 m/s)
- Explain why sound waves cannot be polarised
🎬 Video Resources
- Waves - Overview -- YouTube Search
- Waves - Exam Questions -- YouTube Search
📄 Past Papers & Exam Resources
- AQA A-Level Physics - Waves -- AQA
- Edexcel A-Level Physics - Waves -- Edexcel
- OCR A-Level Physics - Waves -- OCR
🔗 Further Reading & Resources
- Physics & Maths Tutor - Waves -- Free notes, worksheets, and past paper questions by topic
- Dr Frost Maths - Waves -- Free resources, slides, and interactive questions
- BBC Bitesize - Waves -- BBC Bitesize revision resources
📚 Lesson Plan (50 minutes)
- Starter (5 min): Recall prior knowledge of waves with quick questions.
- Teaching (15 min): Work through each of the learning objectives, explaining principles step by step.
- Key points review (5 min): Revisit the key points together, confirming understanding.
- Worked example (10 min): Model the example question: Light of wavelength 500 nm passes through double slits 0.2 mm apart. Fringes observed on screen 2.5 m away. Find fringe spacing. Solution: w = λD/s = (500x10⁻⁹ x 2.5) / (0.2x10⁻^3) = 6.25x10⁻^3 m = 6.25 mm
- Practice (10 min): Students attempt the practice questions independently; circulate and support.
- Plenary (5 min): Review answers and address misconceptions.
🏠 Homework
- A wave travels at 340 m/s with frequency 170 Hz. Find wavelength
- Two coherent sources 1.5 mm apart produce fringes 4 mm apart at 3 m. Find λ
- Find critical angle for glass-air interface (n_glass = 1.5)
- A police siren at 800 Hz approaches at 30 m/s. Find frequency heard (v_sound=340 m/s)
- Explain why sound waves cannot be polarised
🧾 Assessment
Check practice answers against the model answer; use the built-in practice questions as formative assessment.