What can't infrared waves travel through?

Answer 1

All electromagnetic waves can move through a vacuum and the do so at the speed of light. Otherwise, the transmission depends on specific details of the material.

Electromagnetic waves travel through other materials to a greater or lesser extent. We say that a material is transparent if the electromagnetic wave travels through it with relatively little absorption. But, most materials have a complex absorption spectrum, meaning that some wavelengths of electromagnetic waves travel with little loss and some with great loss and the dependence of the energy loss on the wavelength is complex.

Water is transparent by popular agreement, meaning light travel easily though clear pure water. But, in fact, for wavelengths of light just outside the visible spectrum, water appears ink black do to its ability to absorb electromagnetic energy.

Most materials have this property of being nonabsorbing

in limited regions and rather significantly absorbing in others.

So, other than a vacuum, there is always some absorption and so an electromagnetic wave can only get through materials which have a wavelength region with little or no absorption.

Answer 2

Lots of things block infrared (IR) light. A very "rough" guide to what blocks IR is this: if you can't see through it, IR can't get through it. Remember that IR radiation is just below the optical wavelengths. Just below visible light is the infrared range, and IR is sort of like visible light except lower frequency (lower energy and longer wavelength). There are a vast number of things that will block IR. Recall the rough guide and consider that stuff that you can't see through will probably block IR, and vice versa. There are exceptions; the guide is not carved in stone. Many exceptions are found in area of window glazing where it is desired to be able to see out but block the heating IR rays and preventing their entry.

Answer 3

Those that are transparent to it. If you were expecting an exhaustive list, sorry, I have other things to do. Here are two examples: air is pretty transparent to infrared, and so is salt (ordinary table salt, sodium chloride).

Answer 4

Radiation will travel through almost anything if its frequency is high enough.