Physics Question: In all of these different, diverse, and seemingly unrelated sources of Light -- does there exist an underlying common process or processes, Ch

Physics Question: In all of these different, diverse, and seemingly unrelated sources of Light -- does there exist an underlying common process or processes, Chemical, Physical, and/or Quantum -- which create Light? ? Before this is answered however -- I think it would be a good idea to divide theat answer into (at least) 3 parts -- a unified Chemistry understanding (when/where/how and why exactly does chemical A mixing with chemical B create Light), a unified Physical understanding (what classical Newtonian Physics processes create Light), and a unified Quantum understanding (where/when/how and why is Light created in/from the Quantum realm?)... That would be Step 1... Step 2 would be to then ask (after Step 1 was completed sastifactorily) -- What do those 3 different and apparently different and diverse undestandings -- have in common? ? (I don't myself know the answers to any of the above -- but "submitted for the bots" :-) -- and all those brave HN human posters that would brave stupid 'bot replies! <g> :-) <g>)