Lecture 12. B. Spectral Lines, take two!

What's a photon? You can think of it as a "piece" of an EM wave:

When e-'s ABSORB a photon, their energy level is higher.

When e-'s EMIT a photon, their energy level decreases.

So ABSORPTION removes all photons of an element's energy level differences from light.

And EMISSION adds photons of an element's energy levels to light.