How does light interact, and travel through Solid matter as matter gets thicker, in width.? In the absorbion, and emission process of light, hitting electrons, I do not really understand that much, about electron energy levels, and how they change when a lot of atoms become molecules, and them those molecules become solid matter. I think eV levels for electrons change when single atoms become molecules, and matter. I need ro get a idea of how eV changes in electrons, as atoms come together in groups in molecules, and solid matter. so if you have a single atom, then add more atoms in a line up to a micron in width, then add more atoms up to a millimeter. How is light going to behave as more and more atoms are added in a line, then becoming a molecules, and then solid matter, and hpw do the electrons eV levels change as more atoms are added. Thank you for your help, anything helps even a few words.