The standard explanation for how Faraday cages work is that the metal mesh from which it is constructed will let through only those photons with sufficiently small wavelengths to fit through the openings.

Wavelengths

If a photon has a long wavelength, it will not fit through the holes in the metal mesh. Instead, it is reflected or absorbed. So, low energy photons, which are associated with long wavelengths, are prevented from entering the cage.

This sounds reasonable.

However, it makes little sense on closer inspection. Why should the fact that a tiny particle is oscillating at a low frequency have anything to do with its ability to penetrate a metal mesh with holes vastly larger than itself?

Pilot waves and momentum

The alternative explanation is that the penetration of photons through the metal mesh of a Faraday cage has nothing to do with wavelengths. It is rather a function of pilot waves and momentum.

All detectable photons have a pilot wave associated with them.

This wave extends out far beyond each photon, and it is this pilot wave that prevents low energy photons from getting through the mesh of a Faraday cage.

Low energy photons have insufficient momentum to push themselves and their associated pilot wave through the mesh.

These are either absorbed or reflected by the mesh.

Low energy photon about to be reflected by a mesh

Higher energy photons have little problem pushing their pilot waves through the mesh.

To keep these out, the opening in the mesh have to be smaller.

Visible light

For visible light, the mesh has to be as fine as the lattice of atoms in order to prevent penetration.

High energy photon pushing itself and associated pilot wave through a mesh

But the mechanisms behind reflection and refraction of visible light is the same as the mechanisms behind the Faraday cage.

Visible light gets reflected, absorbed or refracted by the atomic lattice of glass depending on their momentum.

Radio waves

For radio waves, the mesh of the Faraday cage acts like the lattice of glass. It lets high energy radio waves through, but absorbs or reflects lower energy ones.

In the case of barriers made out of bricks and mortar, we get that visible light is incapable of penetration.

But radio waves go through. Because the lattice of atoms in these materials are ordered in such a way that they obscure the relatively straight path of visible light. But radio wave photons are of a more meandering kind. So they find ways to penetrate the wall.

Low energy radio wave bouncing its way through bricks and mortar

Low energy radio waves bounce their way through the atomic lattice while visible light gets absorbed or reflected.

For a good introduction to pilot wave theory, watch this video.