The left picture shows a number of translucent sheets. The edge of the sheets seems to glow compared to the rest of the body. Why is this?
The right picture some fiber optic cables. The end of the fiber optic cables glow a lot more than the rest of the fiber optic cable bodies. Why is this?
The translucent sheets and optical fibers are being lit from below. Light enters one end with a relative small angle incidence. Once inside the sheet/fiber the light experiences total internal reflections multiple times because it hits the sides of the sheet/fiber with a large angle incidence. It's not until the light gets to the far end of the sheet/fiber that it hits an internal surface at a small enough angle of incidence that it is not totally reflected internally and manages to emerge.
