How to use the speed of light in a medium calculator
Find the speed of light in a material from its refractive index. Enter refractive index in the field above; the speed of light, fraction of c are computed instantly and plotted on the chart so you can see how the answer changes.
Formula
Variables
- n — Refractive index
Worked example
With refractive index = Crown glass, the calculator gives speed of light ≈ 199,861,600 m/s; fraction of c ≈ 0.6666667.
Frequently asked questions
What is the formula for the speed of light in a medium calculation?
Speed of light (m/s) = CLIGHT / n. Fraction of c = 1 / n. Here n is refractive index.
What inputs do I need for the speed of light in a medium calculator?
You need refractive index. Each field is pre-filled with a typical example so you can see how the result responds as you edit the numbers.
How do I use this calculator?
Type values into the input fields. Results and the chart update instantly. Use Reset to restore the example values, Copy results to paste them elsewhere, or Share to copy a link that preserves your inputs.
Is the result exact?
Calculations use standard formulas and double-precision arithmetic, then display about seven significant figures. Real-world measurements carry uncertainty, so treat results as estimates unless your inputs are exact.