Total internal reflection happens when light inside a stone meets a facet beyond the critical angle. The facet then acts as a perfect mirror, and all the light reflects back into the stone.
In more detail
It is how a pavilion sends light back up through the crown. Total internal reflection loses no light. Facets cut too shallow for the critical angle let light out instead.
How we measure it
All four of our light measures treat total internal reflection as lossless. Only the simulator also counts partial reflections at facets where light can escape.
Related terms
- Critical angle: The critical angle is the angle from a facet's normal beyond which light inside a stone reflects totally. It follows from the refractive index: θc = arcsin(1/n).
- Refractive index: Refractive index is the speed of light in a vacuum divided by its speed in the stone. A higher index bends light more where it crosses a surface at an angle.
- Fresnel reflection: Fresnel reflection is the share of light that a surface reflects instead of letting through. The Fresnel equations give that share from the two refractive indices, the angle and the polarization.
- Leakage: Leakage is light that enters a stone and leaves where the viewer cannot see it, mostly through the pavilion. Lower leakage is better.