system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5- What happens when photons hit a molecule?

I know photons are incredibly small and moving very fast, but what happens when it hits a molecule or atom? I know it happens everywhere that’s why we have visible light. But what happens to the molecule? Does anything dramatic change or happen to it?
gpt
Depending on the energy of the photon there are a couple of options -

"Nothing". Of course nothing would violate laws of physics, so the photon would be reflected (or absorbed) and the molecule would be pushed. ( A tiny amount. Enough that you could propulse a starship with huge sunsails in space, but to less to be noticeable in common situations)

A electron of an atom could be pushed into a higher orbit, or completely out of the atom.
That could lead to effects like photovoltaic cells or plants are using, or others...

A bond between atoms could be broken up, that would lead to molecule degrade. This needs more energy in photons, ultraviolet light has enough.

The effects of this can lead to skin cancer (if the body isn't able to repair all damages to all molecules, especially if DNA molecules are hit) or e.g. printed colour bleaching in the sun.

Lastly, parts of atoms could be be kicked out the atoms. Energy for this would need x-ray or radioactive radiation at least.