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Specification: AQA A-level Physics (7408) 3.3 Waves  |  Paper: 1  |  Data and formulae booklet: given in the exam

Every equation in section 3.3 has its own page: key definitions, the equation with units, and 10 ramped questions from core to stretch, each with a full worked solution.

🛒 All the equations in one place: the AQA A-level Every Key Equation PowerPoint has 127 equations, 381 practice questions and 15 derivations, for £12.

Progressive and stationary waves (3.3.1)

• Wave speed: c = fλ and f = 1/T (3.3.1.1)
• Phase difference (3.3.1.1)
• Stationary waves: f = (1/2l)√(T/μ) (3.3.1.3)

Refraction, diffraction and interference (3.3.2)

• Young’s double slit: w = λD/s (3.3.2.1)
• Diffraction grating: d sin θ = nλ (3.3.2.2)
• Refractive index: n = c/cₛ (3.3.2.3)
• Snell’s law: n₁ sin θ₁ = n₂ sin θ₂ (3.3.2.3)
• Critical angle and optical fibres: sin θc = n₂/n₁ (3.3.2.3)

Examiners name confusing phase difference with path difference, and measuring the critical angle from the surface instead of the normal.

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