If both radio waves and gamma rays can travel through walls

Question

and they are on opposite ends of the electromagnetic spectrum, then why can't light travel through walls which is right in the middle of the spectrum?

This question has already been asked here. However, I am not entirely satisfied by the answer given on that page which relies on fanciful analogies and metaphors of ants, elephants etc. I am looking for a better explanation.

I think the crux of the matter, and my dilemma, relates to formula for penetration depth. This is a well known formula used to explain the fact that low frequency waves have more penetration than high frequency waves.

But then how come gamma waves have such high penetration?

Are there some assumptions behind derivation of this formula which break when we consider very high frequency waves?

Or, are there some new factors that need to be taken into account as we move into the high frequency regime?

Could it be that maybe there are no assumptions behind the formula that break down when considering very high frequency waves, but we need to consider gamma waves as particles in order to fully understand their penetration through matter?

If given a radio source and a gamma source of equal intensity, then will the radio source have more penetrability than the gamma source per formula for penetration depth? If not, why not?

Answer 1

The anthropocentric explanation is that if visible light rays could go through wood or plaster we would not build walls with wood or plaster.

Answer 2

Photons interact with matter if the matter offers quantum transitions that match, or nearly match, the photon's energy in the inertial frame of the matter. Ordinary matter such as wood, stone, etc offer several groups of possible quantum transitions.

1. Rotation of molecules (if they are free to rotate, ie not condensed matter)
2. Vibration of molecules - bending, quivering actions
3. Electronic excitations
4. Nuclear excitations (there being various kinds, ignored here for simplicity)

Microwaves have such low energy, they can't do much, though they might excite some types of vibrations on larger floppier molecules - however any type of molecule that could be described as "floppy" probably isn't good for construction materials. Rotational modes aren't possible in a strong material made of crosslinked polymers or silicates. So microwaves mostly fly right through.

Near infrared and visible light can kick electrons into higher molecular orbitals. Even if the energies aren't a match, just close, there is interaction as Heisenberg lets them cheat temporarily. Also, having more energy, visible light photons can stir up a greater variety of vibrational modes. There's nothing in common wall materials to prevent that, and in fact the interaction with photons is so strong that the material, if not super-thin (microns) will be opaque. Of course, glass is an exception.

Gamma rays are of such high frequency, electrons (or ions, or polarized ends of molecules) can't keep up due to inertia. So no interaction, or only a little. At the right frequencies, gamma photons can interact with nuclei, but for a randomly chosen source of gammas, it's photons are unlikely to match close enough with any of the available nuclear excitations, and can't really do much at the molecular level, the material is almost transparent.

All this is so oversimplified...

Answer 3

A high energy electron can go through a wall. A bull dozer can go through a wall.

But a small dog cannot go through a wall.

Same difference.

Further, radio waves can't go through a metal wall, only a wall made of an insulator.

Gamma ray going through a wall does damage to the wall on the microscopic scale, like the bulldozer. Light is heigh enough energy that it "bounces off" even an insulator, (radio waves "bounce off" metal walls.)