Physics
Atomic Spectra
Quick fact
The bright yellow glow of sodium vapor lamps comes from just two very close spectral lines at 589.0 and 589.6 nm—so distinct that they can be used to identify sodium in distant stars.
Why this is interesting
You've seen neon signs glowing in distinct colors, or a rainbow created by sunlight through a prism—but why does each element produce its own unique set of colors? What secret code do these lights reveal about the atoms themselves?