Grade 11 · Physics
Refraction & Snell’s Law
Why it matters
Bending light and total internal reflection.
Core20m readingPrerequisite: Curved Mirrors
What is refraction and Snell’s law?
Short answer
Refraction is the bending of light as it passes from one medium into another because its speed changes. Snell’s law quantifies it: n₁ sin θ₁ = n₂ sin θ₂, where n is each medium’s refractive index and θ the angle from the normal. Light entering a denser medium bends toward the normal; beyond a critical angle it undergoes total internal reflection.
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Frequently asked questions
- Why does light bend when it enters a new medium?
- Its speed changes; the change in speed at the boundary alters its direction, which we see as bending.
- What is total internal reflection?
- When light in a denser medium hits the boundary beyond the critical angle, it reflects entirely instead of refracting out.