IGCSE Physics: Refraction Calculations — Snell's Law | Edexcel Modular | Unit 5 | L8

IGCSE Physics: Refraction Calculations — Snell’s Law | Edexcel Modular | Unit 5 | L8

This lesson covers spec point 5.18 — knowing and using n = sin i ÷ sin r to calculate refractive index, angle of incidence and angle of refraction.

PowerPoint includes:
• Retrieval starter reviewing practical data from L7
• Direct Instruction (I Do) — Snell’s Law introduced; formula triangle shown; two fully worked examples (finding n and finding r using inverse sine)
• Guided Practice (We Do) — three scaffolded problems: finding n, finding r, and finding i (reverse rearrangement)
• Independent Practice (You Do) — Edexcel-style questions including semicircular block, optical fibre, and i = 0° edge case
• Refractive index concept check MCQ (n = 2.0 meaning)
• Misconception check: can n be less than 1.0? (true/false with reasoning reveal)
• Review and Reflect traffic light on calculator sin⁻¹ usage

Activity Sheet includes:
• Formulae box showing n = sin i ÷ sin r (base formula only, no rearrangements)
• 11 exam-style questions of increasing difficulty
• Questions covering finding n, finding r, finding i, unit conversion, and conceptual understanding
• Stretch question addresses glass-to-water scenario (correctly flagged as beyond IGCSE)
• Full mark scheme with full working for teacher use