A relection on Technology

Okay, so this image is only vaguely related to the subject matter here. It shows dispersion of white light into it's constituent colors.

Light passing through a glass prism.

To explain fiber optics, it is necessary to start at the beginning. When light passes through something more dense than air, it is refracted, that is what makes ponds seem shallower than they are, and leads to illusions like this:



The pencil appears bent because the light from it is bent, that is, the trajectory is altered.

This is what is happening:



What happens if the angle of incidence is increased? There will come a point when the emergent ray just creeps along the interface. What happens when the angle of incidence is increased even further?

THIS:



The right-most example is what happens - the light beam is completely reflected.
100% reflection, unlike ordinary mirrors,which absorb some of the light, Total Internal Reflection reflects ALL the light.

Scientists of the digital age realised that this could be the basis for very efficient communication, in that a light beam (laser) could be reflected like this many times along a glass tube, thus:



Pluses: Loss of information zero; noise, zero.

Minuses: Optical cable is expensive.

In short, fiber-optic technology utilises perfect mirrors. Yet another application of lasers Normal light does not work because it has a finite coherence length (more about that later)

All done with mirrors.