Exploring Thermal Light: The Candle Flame Mystery

[Jules18]

Imagine you're lighting a candle, and it emits yellow light. Because the candle flame is hot, the light is probably thermal (not atomic) in origin. Right?
If you made a spectrum of the candle light, it would appear to be continuous, and that would confirm experimentally that the light was thermal in origin, or so my teacher tells me. But I have no idea why.

I think I get the gist of atomic light. The way I understand, electrons in a certain type of atom absorb light of certain frequencies and then rerelease light of the same frequencies. (eg: neon burns red)
But what's thermal light??
This whole concept drives me crazy.

 

[maverick_starstrider]

Everything your teacher has told you is correct. "Atomic" light is the name for photons that are released when an electron undergoes a quantum leap between orbitals which are quantized and thus you only see specific discrete wavelengths emitted. "Thermal" light is photons that come from the blackbody radiation of an object (http://en.wikipedia.org/wiki/Blackbody_radiation)

 

[Jules18]

Thank you, that link was helpful.

 

[Bob S]

Yellow candle light, red neon light, and yellow sodium light (actually a doublet) are characteristic atomic emission lines of the specific atoms in question. For real thermal emission spectrum, heat a piece of steel with a torch to a red glow, or look at the filament of an incadescent light bulb as a function of input current.

 

[Jules18]

OK I'm not sure that's true, but thanks for the input.

 

[maverick_starstrider]

I'm pretty sure most of the light from a candle is going to be entirely blackbody. Evidenced by the fact that flashlights (which use a heated metal element) and candles give off the same kind of light and furthermore that candles can be made of a number of differnet substances