Light pipes and fiber optic flashlight.

Light pipe and fiber optic flashlight. An incandescent lamp sends light down a spiral made of transparent Lucite rod. Almost all of the light comes out the end of the spiral due to total internal reflection. I.E.: the light traveling through the plastic hits the rod wall at an angle greater than the critical angle and thus is reflected inside the plastic. There is also a flashlight attached to a bundle of flexible fiber optic cable. When the flashlight is turned on, the cable can be coiled or flexed, but still emits light at the tip. Ref: Modern College Physics by Harvey White, 6th ed., p.495-497