Re: How does heating yield white when the object is limited to certain photons

Grant,

Your confusion is completely understandable. At the heart of the matter is the difference between color temperature and the color/spectrum of light. These are actually two related, but different, phenomena. Hence, the reason for the confusion.

When scientists discuss color temperature, the color refers to the visual appearance of the source, assuming the source is a black body. This will only accuratly describe the spectrum of the source if it is a black body radiator. In the case of non-black bodies, such as light bulbs, the absolute temperature (or color temperature) is an approximation of a black body, and that's why the spectrum won't be filled.

I found a neat java tool on the Molecular Expressions Microsopy Primer web site that illustrates color temperature very nicely. Also from this page, I found the following example of this black body/light spectrum discrepancy:

"In cases where a light source, such as a fluorescent lamp, arc-discharge burner, laser, or gas lamp, does not have a spectral distribution similar to that of a black body radiator, its color temperature alone is not a reliable means of selecting suitable filters or creating look-up tables for color balance corrections. Therefore, although two different light sources may be described as having the same color temperature, exposed photographic emulsions or digital images lacking proper white balance baseline adjustments may respond differently to the sources. When using fluorescent lamps or similar light sources, a per-wavelength comparison of sensitivity and spectral output is often necessary in order to determine the correct filters for color temperature balance."

Hope this helps,
Amber