Light From Heat

Why do chemicals have to be heated in the flame first before the colored light is emitted?
- stefano (age 17)
quezon city,philippines

Light carries away energy. At room temperature atoms sit in their lowest-energy state most of the time, so they don’t have any energy to give to light. When they’re heated, the atoms spend some time in higher energy states, from which they can emit light while falling back down to the low-energy states. "Being hotter " and "having a better chance to be in higher energy states" turn out to actually just be different words for the same thing.

Mike W.

(published on 10/22/2007)