Reflection & Refraction
Year 8 🌊 Waves & Optics Apply laws of reflection; understand refraction at boundaries.
🪞 Reflection (Review & Deeper)
When light hits a surface, it bounces back. Specular reflection happens on smooth surfaces (mirrors); diffuse reflection happens on rough surfaces.
| 🪞 Type | 📝 Surface | 🔍 Result |
|---|---|---|
| Specular | Smooth, flat (mirror) | Parallel rays remain parallel → clear image |
| Diffuse | Rough, uneven (paper, wall) | Rays scatter in all directions → no image |
🔭 Refraction of Light
Refraction is the bending of light as it crosses the boundary between two materials of different optical density (e.g., air and glass).
| 🔦 Direction | 💡 Speed changes | ↩️ Bending direction |
|---|---|---|
| Air → Glass (denser) | Slows down | Bends TOWARDS the normal |
| Glass → Air (less dense) | Speeds up | Bends AWAY from normal |
| Along the normal (0°) | Changes speed | No bending at all |
🌈 Dispersion — Splitting White Light
White light is a mixture of all visible colours. When it passes through a prism, different colours refract by different amounts — producing a spectrum.
🔴 Red → 🟠 Orange → 🟡 Yellow → 🟢 Green → 🔵 Blue → 🟣 Indigo → 🟣 Violet
Red = longest wavelength, lowest frequency, least refraction
Violet = shortest wavelength, highest frequency, most refraction
Snell's Law: n₁ sin θ₁ = n₂ sin θ₂