Total Internal Reflection

Ever wonder why diamonds seem to sparkle so much more than other stones? It’s not just because they’re expensive — it’s thanks to a phenomenon in physics called total internal reflection. This occurs when light hits the inside surface of a material, like diamond, at just the right angle and bounces around inside instead of passing through. The result? Light gets trapped, bounces around, and finally escapes in a burst of brilliance, making diamonds glitter intensely.

Here’s how it works: when light moves from a denser material (like diamond or glass) into a less dense material (like air), it usually bends — this is called refraction. But if the angle is steep enough, instead of bending out, the light reflects completely back into the material. That’s total internal reflection. Think of it like light hitting the inside of a mirror instead of leaking out.

Jewelry makers cut diamonds specifically to take advantage of this. They design the angles so that light entering the stone reflects multiple times inside before finally exiting at the top — right into your eyes. That’s why diamonds sparkle so brightly under lights, while a glass bead might look flat or dull. It’s physics, not just beauty.

This same principle is used in fiber optics, which are the thin glass strands that carry internet data. Light bounces down the cable using total internal reflection, letting it travel long distances without escaping. So whether it’s the sparkle of a diamond or the speed of your Wi-Fi, you’re seeing the hidden brilliance of a simple law of light in action.