Flexible light pipe using arc lamp.

Flexible light pipe using arc lamp. White light from a carbon arc is sent through a water cell to eliminate infrared (heat) and is focused onto the tip of a flexible light pipe. The light pipe is made up of a large number of long thin glass fibers bound together in a cable, with the ends polished flat. Light enters the fibers and hits the glass walls at an angle greater than the critical angle, causing total internal reflection with very little loss. The light pipe can be bent and aimed at different parts of the class. The intensity of the beam is amazing. Ref: Modern College Physics by Harvey White, 6th ed., p.495-497