Light Polarization

is a phenomenon I still have no explanation for. (there are of course many more of those!)

Everybody knows the effect of a polarization filter. It enables you, among other things, to take a picture through a closed window without annoying reflections. It also reduces sun glare.

The most intriguing effect is shown by a very old film clip by the renowned scientist sir Lawrence Bragg.

What I find really puzzling is the experiment where a light beam appears or disappears, not totally, that would be still explainable, but only in the horizontal or vertical direction. (around the 9th minute)

With the use of a mirror Bragg shines a beam through a liquid tank and we can see the beam going through the tank and being reflected by the mirror.

But then, and that is a complete mystery to me, by using polarizing filters, he makes the beam shine only through the water, but not on the mirror. Or vice versa.

The explanation Bragg gives is more confounding than anything else.

It has, he says, to do with vibrations perpendicular to the direction of the beam. The filter allows sometimes horizontal, and other times vertical vibrations. And that would explain why we sometimes see the beam, and sometimes not.

This is a very peculiar model of vision that is only used when dealing with polarization. In all other cases, scientists prefer the model in which light rays go into the eye directly.

The problem with this last model is that it would be of no help at all. After all, saying that we do not see the beam because the rays are not reaching our eyes, would not be very helpful.

What we want to know, is why the rays are not reaching our eyes. In fact, we would like to know even why the rays are reaching our eyes when the beam is directed in another direction.

The idea is that, somehow, there are rays, or waves, sometimes reaching our eyes, and sometimes not. Even if they remain invisible unless they impinge on our retina.

I do not find this explanation very convincing. If you look at the beams used by Bragg, and laser beams as they are used now, it would be very difficult to believe that anything is propagated sideways.

As I have also indicated elsewhere, since beams that are not directed towards us are visible from very large distances, we would have to assume that each beam, whatever its direction, propagates rays, waves, photons, or whatnot, in all directions.

This would be quite contradictory with the Huygens Principle that states, freely translated, that a light wave can go on indefinitely because everything is at the service of the main wave.

It would also make of vision an unexplained mystery. How can rays that are unable to be reflected off the liquid beyond a certain distance, ever reach our eyes?

Imagine you are submerged in a large swimming pool and you are looking at two people some meters away, shining laser beams at each other.

If we assume that you are able to see those beams as they go through the water, shouldn't you be able to see the rays that enter your eyes and make you see the beams?

Also, Bragg's explanation is really strange as an explanation of vision for the simple reason that vibrations in themselves do not explain vision. Nor do electric or magnetic fields.

We can only see electromagnetic forces when other matter is involved, we never see the force or the field itself.

So, vibrations just don't cut it.

But then, what?

Honestly, I do not know.