Light Traveling Through a Transparent Medium

Transparent materials such as glass and water have a strange ability to let light through as if they were made of nothing. Yet some transparent materials, such as glass, are very dense. They are full of atoms. How can it be that the photons travelling through such materials do not get scattered, or in other ways impaired in their path?

Light leaving a transparent medium is just as focused and sharp as light entering it. There is no loss of direction or energy. There is no fanning out inside the medium.

The only way this can be explained using the Velcro model of the photon is that transparent media are so constructed that all paths through them are well defined meanderings among atoms.

A way to envision this is to think of photons as slalom skiers, and the glass as a slope full of evenly spaced poles in all directions. The rule of the race down the hill is that the skiers have to start with a half roll past the first pole, then full rolls in altering directions down the hill until a final half roll is made on exiting the slope.

The skiers may make a first half roll to the left or the right. It does not matter. However, the next roll has to be in the other direction, and the next roll after that has to be opposite to the previous, and so on all the way down.

For skiers coming into the slope at an angle, the first half roll will either be larger or smaller then average, depending on the angle of entry and which side of the first pole they enter. However, this is perfectly balanced on exit with a corresponding deviation from the average.

This will result in all skiers leaving the slope in the exact same direction that they entered it, provided the first row of poles are parallel to the last row of poles.

Since our skiers are photons, they travel at the exact same speed regardless of their size. They always travel at the speed of light. However, the length of the path travelled by a small photon and a big photon will not be identical.

Small photons roll past the poles with their geometrical centre closer to the poles than the bigger photons, so even when large photons and small photons take the exact same path through a transparent medium, the small ones end up travelling a shorter distance.

Send a red photon and a blue photon through a piece of glass at the exact same time, and the red one ends up exiting the glass ahead of the blue one. The red one has less energy than the blue one. It is smaller, and is therefore rolling past the atoms in the glass at a shorter distance from the atoms' centre than the blue one.

Red and blue photons racing through a piece of glass.

This explains why blue light takes more time to travel through transparent media than red light, even when their paths through it is exactly the same.

It also explains why blue light refracts more through a prism than red light. It explains why a mix of various size photons, known to us as white light, get split into all the colours of the rainbow, with blue light always at the most acute angle from the prism, and red light at the least acute angle.

Photons hitting a wall after travelling through a prism.

Being larger than red photons, blue photons take more time rolling past the first atom. This makes the initial half roll more acute for blue photons than red photons. It also makes the full rolls and the final half roll more acute.

The initial and final half roll of photons are precisely defined by the photons' size compared to the atoms in the medium. The bigger the photons, the more acute are their half rolls into and out of the prism.

Note that the photons do not divert from each other in their overall change in direction on entering a medium. Photons of different colours race through the medium in parallel.

It is not until the final half roll that diffraction happens. If the final half roll is back into the original direction, as is the case with plain glass sheets, the difference in original half roll entering the glass is cancelled out by the difference in half roll on exiting the glass.

However, if the final half roll is to the same side as the original half roll on entering the glass, as is the case in a prism, the original angle does not cancel out. It gets added to, and there is diffraction.

Diffraction happens as photons exit the media, and only when half rolls do not cancel on exit.

This is why there is no refraction in even the thickest glass sheets, while the smallest of prisms diffract light just as well as a big one.

Note also that this has nothing to do with wavelength.

For those familiar with Snell's law, this might seem puzzling. After all, Snell's law can be used to correctly calculate refraction and the apparent slowing down of light in transparent media, yet there is no mention of size in Snell's law. It relates wavelengths, speeds and densities to each other. That's it. Sizes are not included.

The fact that Snell's law applies perfectly to light, is therefore commonly used as "proof" that light must be waves, or possess wave-like properties.

However, Snell's law is no proof of anything regarding the nature of light, because Snell's law is not limited to wavelengths, speeds and densities. It works perfectly well for sizes as well. We have just demonstrated this in the above discussion.

It is the failure to recognize that relative sizes should be included in the list of relations applicable to Snell's law that has introduced wavelength rather than size into formulas for optics, quantum physics and beyond.

Snell's law is a perfectly valid formula. However, it should be extended to include size when dealing with particles. Furthermore, all formulas for photons in which wavelength or frequency appears should be replaced with formulas using the more correct measure of size.

Of course, no such wholesale replacement of physics formulas are likely to occur any time soon, so that leaves it up to those preferring the Velcro model to make a mental replacement themselves. Keep in mind when doing this that big wavelengths correspond to small particles, and visa versa.

Radio-wave photons are very small. Gamma ray photons are very big.