Snell’s Law Calculator
Find the refraction angle with Snell’s law.
How light bends
Snell’s law describes how a light ray bends when it passes between materials of different optical density, such as air and water. The bend depends on the two refractive indices and the incoming angle.
Light hitting water at 30 degrees from air bends to about 22 degrees. If the angle is too steep going into a less dense medium, the light reflects entirely instead — total internal reflection.
Precise and private
The calculation runs in your browser, so nothing you enter is uploaded.
Frequently Asked Questions
What is Snell’s law?
It relates how light bends between two media: n1 times the sine of the incident angle equals n2 times the sine of the refracted angle.
What is a refractive index?
A number describing how much a medium slows light. Air is about 1.0, water 1.33, glass around 1.5.
What is total internal reflection?
When light cannot refract out into a less dense medium, it reflects entirely. The tool flags this case.
Browse the full set of free, private, in-browser tools.