💡 n = refractive index | θ = angle in degrees | Air n≈1.00 | Water n≈1.33 | Glass n≈1.52 | Diamond n≈2.42
📖 How to Use This Refractive Index Calculator
1
Select what to calculate - Choose n₂, n₁, θ₁ (incidence), or θ₂ (refraction).
2
Enter known values - Input the known refractive indices and angles.
3
Click "Calculate" - Get the result with step-by-step solution using Snell's law.
🔆 Understanding Snell's Law
Snell's Law describes how light bends (refracts) when passing from one medium to another. The formula is n₁ sinθ₁ = n₂ sinθ₂, where n is the refractive index and θ is the angle measured from the normal (perpendicular) to the surface.
Total internal reflection occurs when light tries to go from a higher refractive index medium to a lower index medium at an angle greater than the critical angle. All light is reflected back, none is transmitted.
What is the critical angle?
The critical angle is the angle of incidence in the higher-index medium that produces a 90° refraction angle. It's given by θ_c = arcsin(n₂/n₁).
Why does a straw look bent in water?
Light from the straw refracts (bends) as it exits water into air. Your brain interprets this as a bent straw because light appears to travel in straight lines.