There is probably a hermit in a cave someone who has not yet heard the words "fiber optics", but thanks to massive expenditures on technology, installation and marketing by telecommunications companies, most of us are certainly familiar with the phrase. What we likely think of right away are decorative objects, toys and other things that sprout an array of thin fibers that glow at the ends when the device is switched on. Beyond consumer items, such fiber arrays are used in "light pipes" in medical, dental and engineering applications where it is necessary to illuminate something in a space too small to allow use of an in situ light. Very large arrays of optical fiber are even used to deliver daylight to an internal space that has no windows.
When a beam of light travels from a medium of higher into a medium of lower refractive index, it speeds up and this causes the beam to bend further away from the vertical to the surface between the media. If the incident beam is...