system
Given the following post, respond as if you're commenting on Reddit:
human
Why is glass translucent/transparent? Is it a molecular arrangement thing? Is all clear matter clear for the same reason, such as water and diamond?
gpt
In general: Because there is no transition between an occupied and an empty energy level that corresponds to the energy of the light you consider (here: visible light). If there is such a transition, an electron can absorb the photon and reach the higher energy level, but if that process is not possible then the material will be transparent. This is not a binary thing - in general all materials will absorb *some* light, this includes glass and water. A few meters of glass or a few hundred meters of water are barely letting any light through.

The energy levels mainly depend on the molecules in the material and a bit on their arrangement.