Science
Snell's Law Calculator
Use the Snell's law calculator for refraction problems where light bends between two media.
Choose the missing quantity; the calculator hides that field and solves it from the others.
Solved value
—
- Refractive index n1
- —
- Incident angle theta1
- —
- Refractive index n2
- —
- Refracted angle theta2
- —
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Study path
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What the snell's law calculator solves
Use the Snell's law calculator for refraction problems where light bends between two media.
Formula
How to use it
- Choose the quantity you want to solve for.
- Enter the known values with consistent units.
- Check the rearranged formula, substitution, and warnings before using the result.
How to read the answer
Snell's law relates angles measured from the normal line and the refractive indices of the two media.
Common mistakes and edge cases
- Angles are measured from the normal, not from the surface.
- Use refractive indices for the same light wavelength when precision matters.
- If the angle solve has no real value, the setup may be in total internal reflection.
Worked examples
Air into glass
Solved value
Refracted angle theta2 = 19.4712 deg
Find refractive index
Solved value
Refractive index n2 = 1.5013
Frequently asked questions
Can the snell's law calculator solve for a missing variable?+
Yes. Use the solve-for control to hide the missing value, then enter the other known values with compatible units.
Why do the units matter?+
Formula calculators assume the entered values are already in matching units. Convert first when your measurements use mixed systems.
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Last updated: May 15, 2026