If you are still reading this at this point, you might be wondering what more can we learn from rainbow that isn't already known?  Well, you might just be in for a surprise!

The rainbow effect is possible for combinations of media other than water and air.  A classic example is when light passes from air to a prism.  At the University of British Columbia, Dr. Lorn e Whitehead designed a special kind of paper which has micro-prisms stuck onto one side of it.  When held up to the light, it gives off beautiful rainbow colours (see Figure 15).  Taking advantage of the occurence of total internal reflection in prisms, this special paper is currently used as the material for light guide or light pipes.  How the prism paper looks when put up close to an object if shown in Figure 16.  The light pipe is an efficient apparatus for guiding light because a high percentage of the light from the light source is reflected back inside the pipe.  That is, very little light is lost due to refraction off the surface of the pipe.  Consequently, the light from the source is efficiently guided towards a des tination.