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Refractive Index from Speed of Light Calculator

n = c/v — ratio of light speed in vacuum to medium.

Calculates the refractive index of a medium from the speed of light in that medium. Also computes the critical angle for total internal reflection at the medium-air interface.

Dr. Helena Ortiz By Dr. Helena Ortiz
Published Last reviewed 1 min read

Inputs

Results

Enter values and click Calculate to see results.
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How to use this calculator

  1. Fill in the inputs above using the units you already have.
  2. Values update automatically as you type — no submit button needed.
  3. Hover any result row for the underlying formula and intermediate values.

Formula

n = c / v_medium = 3×10⁸ / v; θ_c = arcsin(1/n) in degrees

In depth

Calculates the refractive index of a medium from the speed of light in that medium. Also computes the critical angle for total internal reflection at the medium-air interface.