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I'm looking for a set of examples to illustrate the relation of temperature and color of "glowing" bodies.
It should allow to build an intuitive understanding of this relation, so it's not about spectra, but just color in terms of visual appearance.

The examples should cover infrared to somewhere above visual light if possible (or reasons why it's not possible).


Some good temparature/color-relation-examples froom comments/answers:

An example for about 2500K could be a tungsten wire of an incandescent lamp. It is not a good example because the wire in gas is not a good model for a black-body, as C. Towne Springer explains in his answer.
He provides an an electric kiln as an example for about 1400K giving very good black-body approximation.

As said, it's about the illustration, not about perfectly matching the spectrum of a black body - "similar enough to look the same" would qualify.

From Robin's comment, the sun could be good as example for about 5800K.

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    $\begingroup$ The sun radiates similarly to a black-body with a temperature around 5800 K. More generally the color of a star can tell you how hot it is. $\endgroup$ – Robin Ekman Apr 9 '14 at 2:01
  • $\begingroup$ Does that mean the radiation of a gas at some temperature is similar to that of a black-body at the same temperature in general? $\endgroup$ – Volker Siegel Apr 9 '14 at 2:13
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    $\begingroup$ @VolkerSiegel In general, more or less yes $\endgroup$ – Jim Apr 9 '14 at 17:16
  • $\begingroup$ "Black body" has a pretty rigid definition and that might be holding back answers. If you want intuitive demonstrations of Planck's law you might get more examples. Like feeling the heat from an oven at 200C when you are too far away for convection or conduction. Or a step into the near IR and visible - the heat from an "IR" restive heater. The long bars in reflectors used in otherwise unheated shops perhaps. Then low and high temperature kilns and maybe a gas forge just after the gas is turned off. It is hard to get much hotter in the atmosphere without chemical reactions interfering. $\endgroup$ – C. Towne Springer Apr 10 '14 at 4:25
  • $\begingroup$ Oh, interesting point regarding use of the term black-body. Feel free to edit the question and title to make that better, if you like! $\endgroup$ – Volker Siegel Apr 10 '14 at 5:32
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Most campuses have a ceramics section to the art department. Gas and electric kilns are great for this. At the temperatures called "cone 9" and "cone 10" everything inside the kiln becomes invisible. It is just red-orange inside. The light bulb is a terrible example. The filament in an insulating chamber with a tiny hole is OK as long as the whole chamber gets as hot as the filament.

An optical hot wire thermometer is nice to use for measurements from a pedagogical standpoint. The interior of the oven is viewed and a calibrated filament in the plane a cross-hair would be is heated by an electric current and adjusted until it vanishes against the background. It is quite amazing to see it disapear. A little hotter and it gets more yellow than the oven. (Question to the inquisitive. Why is there no "green hot" temperature range, and therefor no green stars?)

Electric lamps are not filaments in vacuum. They are in pressurized argon. The argon atom is so massive that escaped tungsten atoms have a very high likelihood of being bashed back onto the filament and this keeps it from vaporizing and coating the inside of the glass. There is a strong convection of the gas and this makes it a poor example. For spectra of a hot object, it is passable. A Nernst Glower from an IR spectrophotometer is a lot better.

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  • $\begingroup$ I have edited the title to better convey what I'm looking for, basically more of "Sun: typically 5800K, electric kiln: typically ...K", with a description of the color if not obvious. $\endgroup$ – Volker Siegel Apr 9 '14 at 20:07
  • $\begingroup$ Thanks for noting the (off topic) "hot wire thermometer" - brilliant as experiment, and as application of physics. $\endgroup$ – Volker Siegel Apr 9 '14 at 20:08
  • $\begingroup$ I think they were called an "optical pyrometer" and don't know if they are still used. Solid state IR detectors might have replaced them. A grating and a way to find the wavelength of the peak of the light curve will tell the temperature. Maybe even just a ratio at two wavelengths. I borrowed an optical from Penberthy Electromelt once to check the kilns for the ceramics grad students. (Penberthy also founded Mountain Safety Research, MSR). $\endgroup$ – C. Towne Springer Apr 9 '14 at 23:26

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