Why does light not pass through voids within atoms?? Wow, i luuuuuvvvvv this site. for years i've had a fascination but rarely found many answers on many things. so a BIG thanks to some of you have been answering some of my questions so far. Here's another... When doing a fibre optic course, i asked the tutor why light could not pass through the wall, but could pass through air and glass, as essentially the atoms of the wall are mainly vacuum. I have never had a satisfactory answer to this, and i hold the incorrect opinion that everything of finite density should be allowing light to pass through. now i may be far too inept on the quantum side of things, to ever fully understand why things aren't transparent. but when i think about the space within the atom, my basic understanding tells me light should be passing through the space in atoms in a similar way as it travels between planets in our solar system. note that for this i am addressing light as photons in particle form. an added query following on from this would be that when atoms reflect a wavelength thus giving colour, why do the remaining wavelengths not pass through but are trapped, and what is atomically different between transparent and non transparent atoms.