Why is glass opaque to UV and I guess more energetic radiation?
Why are buildings transparent to radio?
I was told that it is because the particles making up the substances in question are larger or smaller than the wavelength. Is this accurate?
Thanks,
Rob
Well, particle is a bit of a vague concept, but I think it has more to do with crystalline structure rather than particle size. Glass and concrete are both made of atoms of relatively low atomic weight elements: indeed, both are largely silicon and oxygen (though also a fair bit of calcium and carbon in concrete I think).
I won’t attempt an answer, but Richard Feynman’s book QED deals with the question of why light is reflected or passes through glass. Turns out it’s complicated.
I read that several years ago, but I don’t remember how it explained that glass was transparent to light. In terms of summing up vectors, I don’t see how it explains why glass is transparent to light but opaque to UV.
Thanks,
Rob
Opacity can derive from two effects: light scattering (dependent on particle size for non-homegenous solids such as concrete) and light absorption (depending on the molecular composition). Which wavelengths of light are absorbed by a substance depends on its molecular structure, which determines the energy level of its electrons. If the wavelength of the incident light corresponds to the energy difference between an occupied electron orbital and a non-occupied higher energy orbital for the same electron, the light can be absorbed and the energy used to shift the electron to the higher energy orbital.