Free Critical Angle Calculator

Calculate the critical angle for total internal reflection: theta_c = arcsin(n2/n1).

Critical Angle

41.81 °

Critical Angle vs Denser Medium Refractive Index

Critical Angle

The critical angle is the angle of incidence above which total internal reflection occurs when light travels from a denser to a less dense medium.

Formula

theta_c = arcsin(n2 / n1)

where n1 > n2. Above this angle, no light passes through the boundary.

Example Calculation

Light going from glass (n=1.5) to air (n=1).

  1. 01theta_c = arcsin(n2/n1)
  2. 02theta_c = arcsin(1/1.5)
  3. 03theta_c = arcsin(0.667)
  4. 04theta_c = 41.81°

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