How come light only reflects off surfaces and not internal planes?

[jeebs]

When light approaches and enters a material, why does all the reflection happen at the surfaces? I mean, light is coming at say, some crystalline solid. It hits the first plane of atoms and some is reflected. Some goes into the crystal and passes through the 2nd, 3rd, 4th,..., (n-1)th plane of atoms completely unreflected. Then it hits the far boundary (the nth) plane of atoms and some gets reflected. What is so special about the front and back planes of atoms?

[Dr Lots-o'watts]

Light gets reflected from all the planes. Only the deeper it is, the less light there is left because of absorption, or skin depth. For a metal, this layer is very thin, so only the planes near the surface are relevant.

[Bob S]

Many x-ray spectrometers use Bragg diffraction (or reflection), nλ = 2d sin(θ), off the crystal planes; quartz 310, silicon 111, among others.

Bob S

[jeebs]

ahh Bragg diffraction of course, I remember that...

[Dadface]

There tends to be greater light reflection at boundaries between different media where there is a change of refractive index.

[MagnetDave]

Analogously - why does sound only reflect off the walls, not each "layer" of atmosphere it's traveling through?

Part 1 - It does.

Part 2 - The effect of reflection from an impedance boundary is vastly greater than the effect of scatter in the bulk of the material. The difference is sufficient to ignore for almost all applications.