Explore the Light Refraction Simulator
Bend a light ray between air, water, glass and diamond and find the critical angle. Free, no signup, runs in your browser.
- Free to use
- No signup
- Nothing to install
- Runs in your browser
Illustration. Open the tool for the real thing.
See it in action
The Light Refraction Simulator with sample data entered and the result showing.
What is the Light Refraction Simulator?
Bend a light ray between air, water, glass and diamond and find the critical angle. It runs in your browser, so a change to a setting or a drag on an object shows up at once.
Lenses in glasses, cameras and microscopes rely on refraction, and optical fibres carry the internet by total internal reflection. Swimmers see the pool bottom shifted because of refraction.
3 steps to your result
Open the tool and follow along. Nothing to install.
What you get
Snell's law: n1 sin θ1 = n2 sin θ2.
Light bends toward the normal when entering a higher-index material.
Total internal reflection happens when going to a lower index above the critical angle.
Send light from glass into air and find the critical angle.
Compare water and diamond.
Use a bigger incident angle to see total internal reflection.
Used for
Pick one to see how it fits.
Physics learners
Physics students in middle school, high school and first-year university, teachers who want a quick demonstration for the projector, and anyone revising for exams.
Try it freeTeachers
For teachers: project the Light Refraction Simulator (Snell's Law) on the board, let students predict the result, then run it together and test this: Compare water and diamond. For students: change one thing at a time and write down what changes.
Try it freeHow it compares
A plain look at this tool next to the usual alternative.
| This simulation | Textbook diagram | |
|---|---|---|
| Interactive | Drag, tap and change settings | Fixed picture |
| Install | Nothing to install | Not needed |
| Cost | Free to use | Depends on the book |
Questions people ask
What is the critical angle?
The incident angle above which light going into a lower-index material cannot refract and is entirely reflected. It equals arcsin(n2 / n1).
What is a refractive index?
The ratio of the speed of light in a vacuum to its speed in the material. Air is about 1.00, water 1.33, glass about 1.5 and diamond 2.42.
Is the Light Refraction Simulator (Snell's Law) free to use?
Yes. The Light Refraction Simulator (Snell's Law) is free, needs no signup or download and runs in your web browser. It is part of the Physics group of AZRS simulations.
Does the Light Refraction Simulator (Snell's Law) work on a phone or tablet?
Yes. The Light Refraction Simulator (Snell's Law) takes touch input as well as mouse input, so you can use its 14 adjustable settings with a finger. A larger screen makes the controls and graphs easier to read.
How do I use the Light Refraction Simulator?
1. In the Light Refraction Simulator (Snell's Law), use the controls to change Top material, Bottom material, Laser angle from the normal, Light wavelength (colour), Light, and more. The simulation reacts instantly. 2. In the Light Refraction Simulator (Snell's Law), pick an option such as Two materials (interface), Slab in surrounding material, Air, Vacuum to switch modes or load an example. 3. In the Light Refraction Simulator (Snell's Law), press "Go to critical angle", "Reset" to start, reset or change what is happening. 4. Start with this experiment: Send light from glass into air and find the critical angle. Drag any glowing handle, object or slider with your mouse or finger and the Light Refraction Simulator (Snell's Law) responds in real time. 5. Change one setting at a time and watch which readout moves, then compare it with this idea: Snell's law: n1 sin θ1 = n2 sin θ2.
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Bend a light ray between air, water, glass and diamond and find the critical angle. Free to use.
Try it free