Snell's Law Calculator Formula
Understand the math behind the snell's law calculator. Each variable explained with a worked example.
Formulas Used
Angle of Refraction
theta2 = asin(n1 * sin(theta1 * pi / 180) / n2) * 180 / piVariables
| Variable | Description | Default |
|---|---|---|
n1 | Refractive Index 1 | 1 |
theta1 | Angle of Incidence(°) | 30 |
n2 | Refractive Index 2 | 1.5 |
How It Works
Snell's Law
Snell's law describes how light bends when passing between media with different refractive indices.
Formula
n1 * sin(theta1) = n2 * sin(theta2)
Light bends toward the normal when entering a denser medium (higher n) and away from the normal when entering a less dense medium.
Worked Example
Light enters glass (n=1.5) from air (n=1) at 30 degrees.
- 01n1*sin(theta1) = n2*sin(theta2)
- 021*sin(30°) = 1.5*sin(theta2)
- 030.5 = 1.5*sin(theta2)
- 04sin(theta2) = 0.333
- 05theta2 = 19.47°
Frequently Asked Questions
What is the refractive index?
The ratio of the speed of light in vacuum to the speed of light in the material. Air: ~1.0003, water: 1.33, glass: 1.5, diamond: 2.42.
What causes a rainbow?
Sunlight refracts when entering water droplets, disperses by wavelength (Snell's law gives different angles for different colors), and refracts again on exit.
What happens when light goes from dense to less dense?
The refracted angle is larger than the incident angle. Above a critical angle, total internal reflection occurs.
Learn More
Guide
Understanding Optics and Lenses
A complete guide to optics and lenses. Learn about refraction, Snell's law, converging and diverging lenses, the thin lens equation, magnification, mirrors, and optical instruments.
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