Total Internal Reflection: Light Trapped in Glass

Total internal reflection happens when light hits a boundary at too steep an angle to escape.
Instead of passing through, the light reflects completely back inside the material.
This effect requires light to move from a denser medium, like glass or water, to a less dense one, like air.
The critical angle is the exact minimum angle needed for total internal reflection to occur.
Fiber optics use this principle to trap light and send data across the world.
Diamonds sparkle so brilliantly because of total internal reflection inside their facets.
Periscopes and binoculars often use prisms that rely on total internal reflection instead of mirrors.
This phenomenon is lossless—no light energy escapes, making it very efficient.
Snell’s Law helps predict when total internal reflection will take place.
Without it, modern communications, medical imaging, and even gemstone brilliance would be impossible.