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Critical Angle for Total Internal Reflection Calculator

θ_c = arcsin(n₂ / n₁), valid only when n₁ > n₂.

Compute the critical angle of incidence at which light travelling from a denser medium (n₁) into a rarer medium (n₂) undergoes total internal reflection: θ_c = arcsin(n₂ / n₁).

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

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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

θ_c = arcsin(n₂ / n₁), only when n₁ > n₂.

In depth

Compute the critical angle of incidence at which light travelling from a denser medium (n₁) into a rarer medium (n₂) undergoes total internal reflection: θ_c = arcsin(n₂ / n₁).