What this calculator does
Snell's law of refraction works out angle of refraction as light passes between two media. Enter your own figures above and the answer updates as you type: nothing is fixed in the code, so the result reflects exactly the numbers you supply.
The formula this calculator evaluates is printed under the tool and explained below, so you can check the working by hand or reuse it in a spreadsheet.
The formula
Formulan₁sinθ₁ = n₂sinθ₂
The inputs explained
| Field | What to enter |
|---|---|
| Refractive index of medium 1 | A number. Starts at 1. |
| Refractive index of medium 2 | A number. Starts at 1.33. |
| Angle of incidence (°) | A number, measured in °. Starts at 30. |
Worked examples
Every figure in the tables below is produced by this page’s own calculator at build time, so the numbers and the tool always agree. Select any row to load that scenario.
How the answer changes with refractive index of medium 1
Every other input is held at the calculator’s starting values while refractive index of medium 1 varies. Select any row to load that scenario into the calculator.
How the answer changes with refractive index of medium 1
| Refractive index of medium 1 | Angle of refraction | Speed of light in medium 1 | Speed of light in medium 2 |
|---|---|---|---|
| 0.5 | 10.834° | 599,584,916 m/s | 225,407,863 m/s |
| 0.75 | 16.377° | 399,723,277 m/s | 225,407,863 m/s |
| 1 | 22.082° | 299,792,458 m/s | 225,407,863 m/s |
| 1.5 | 34.327° | 199,861,639 m/s | 225,407,863 m/s |
| 2 | 48.753° | 149,896,229 m/s | 225,407,863 m/s |
| 3 | Total internal reflection: no refracted ray | 26.32° | 1.128 |