As I understand it, the only real difference between radio, visible light, x-ray and everything in between is its wavelength. For instancew, radio has a very long wavelength, x-ray very short, visible in the middle somewhere. This means that radio can penetrate stuff (matter?) more effectively, among other things.
Radio waves are (essentially?) harmless, but shorter wavelengths are famously more dangerous, from sunburn all the way to straight up cancer and so forth. Why is that?
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You are already familiar with different types of EM radiation interacting with some things but not with others. Light can travel through air, glass, but not humans, wood or any other solid objects or certain liquids. You also can see light partially interact with things, like water only letting light penetrate so far and absorbing different wavelengths (seen as colors) at different rates.
The same is true for all of EM radiation. Radio waves can partially pass through building materials and travel long distances through air. X-rays travel mostly through tissue, but not through bone.
The reason why EM radiation reacts with certain things and not others is *quant*um mechanics and chemistry. Energy (like a photon of EM radiation) comes in packets of discrete value/size/*quant*ity. Meanwhile, every bit of matter is at some energy state or level *and* every bit of matter has a whole range of energy states it can be at, but it can’t be just *any* level. The energy states for matter are also *quant*ized.
You can picture this like a step on a set of stairs and we can label them sequentially – let’s use the alphabet, A to Z. If something is at energy level A, it takes a certain amount to get up to Step B. It’s measurable. A specific *quant*ity. And each step is slightly different than the last. Generally, the ‘distance’ of those steps get smaller at higher energy states.
For something to absorb or interact with energy (EM radiation), that packet of energy has to take you from one step to another – there are no half steps. It can be from Step A to Step B, or Step F to Step G, or from Step C to Step Q. This is pure absorption of that energy. If the incoming energy doesn’t match an energy step, then that energy doesn’t interact with the matter and passes through.
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