3. applied when craving diamonds or stones to ensure that they would reflect light and shine.
4. Fiber optics:
A fiber optic is a glass "hair" which is so thin that once light enters one end, it can never strike the inside walls at less than the critical angle. The light undergoes total internal reflection each time it strikes the wall. Only when it reaches the other end is it allowed to exit the fiber.
Fiber optic cables are used to carry telephone and computer communications. Advantages over electrical wired include:
Fiber optics can carry much more information in a much smaller cable.
No interference from electromagnet fields result in better connections.