Physics

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Angle of Refraction Calculator.

Apply Snell's law to find the refracted angle.

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refractionAngle: 19.471221

refractionAngle

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Use Cases

Physics homework and exam prep

Quickly verify your manual Snell's law calculations for optics problems involving refraction at a boundary between two media.

Example: Find the refracted angle when light passes from water (n=1.33) to glass (n=1.5) at an incident angle of 30°.

Optics and lens design

Estimate how light bends when entering different materials, useful for designing lenses, prisms, or optical fibers.

Example: Calculate the refracted angle for light entering a diamond (n=2.42) from air at 20°.

Frequently Asked Questions

How do I use the Angle of Refraction Calculator?
Enter the refractive index of the first medium (where light is coming from), the refractive index of the second medium (where light enters), and the incident angle in degrees. The calculator applies Snell's law to compute the refracted angle.
What is Snell's law?
Snell's law relates the angles of incidence and refraction to the refractive indices of two media: n1 * sin(θ1) = n2 * sin(θ2). The calculator solves for θ2, the refracted angle.
What if the calculator shows an error?
If the incident angle is greater than the critical angle (when light moves from a denser to a rarer medium), total internal reflection occurs, and no refracted angle exists. Ensure the incident angle is within the valid range.

Tips & Common Mistakes

Tips

  • Ensure the incident angle is measured from the normal (perpendicular) to the surface, not from the surface itself.
  • Use the correct refractive indices for your media; common values are air (1.00), water (1.33), and glass (1.5).
  • If the refracted angle is 90° or greater, check if total internal reflection occurs; the calculator may not provide a valid result.

Common Mistakes to Avoid

  • Entering the incident angle in radians instead of degrees; the calculator expects degrees.
  • Swapping the refractive indices of the first and second media, which changes the result.
  • Using the angle from the surface instead of the angle from the normal.

Last updated: August 13, 2026