In article >,
"Oscar_Lives" > wrote:

> Just out of curiosity, what entity emits the highest-intensity
> [intensity is measured in photons-per-second-per-square-meter] of EM
> radiation at wavelengths in the range of 3,000 to 100,000 nm [IR-C
> spectrum] yet at the same time emits the lowest-intensity of EM
> radiation outside of the IR-C range?

For intensity, the photons must be weighted by their energy which is
proportional to frequency. Photon count by itself is inadequate.

The question you ask is difficult to answer. The spectral emissivity of
a substance varies with temperature or other conditions. For example, a
xenon flashtube is obviously pretty transparent to infrared and visible
light. Heat it up enough with a discharge and it starts to resemble a
black body. Almost all substances when heated up enough will look like a
black body.

One of Einstein's insights was to explain the law of Dulong & Petit.
regarding the temperature dependence of specific heats. In doing so, he
helped quantum mechanics get going to develop to a point that he denied
quantum mechanics in a way reminiscent of how some deny special
relativity on this newsgroup.

That aside, as temperature increases various modes of vibration of
molecules, atoms, ions, and even bound electrons get excited. These are
able to absorb and emit light.

Perhaps a Welsbach mantle is a good example for selective emission in a
solid. The original mantle consisted of a burned silk fabric containing
thorium oxide with some cerium oxide. The thorium was relatively white
throughout the near infrared and visible spectrum. Because thorium oxide
emissivity was low, it was possible for the mantle to reach a
temperature close to the flame temperature. When cerium oxide was added,
energy was encouraged to escape radiatively in the visible because the
cerium oxide had absorption lines there.

More recently, because of concern over radioactivity, thorium in the
mantles has been replaced by other elements. I believe yttrium oxide is
virtually transparent to near infrared and visible radiation.

Bill

--
An old man would be better off never having been born.