I refer to the opposite effect in this case Harry. In other words, can the color appear to be too dark in the visual region to our eyes compared to the emission of thermal energy in the IR.
Are there surfaces that are very poor emitters of energy in the visual region that behave more like a black body in the infrared region? This is more of a question instead of a statement since it seems like that might be happening in this special case. The light emitted does not have a color that matches what is expected to be seen from a surface of a broad band black body. I wonder if anyone on the list has seen materials with that characteristic. If you consider the behavior of a RF radio transmitter, you will understand the jest of my question. In that case, the amount of power at its transmission frequency, being narrow band and so low in Hertz, would indicate a black body that was at an enormous temperature if the complete spectrum were available as expected. But we know that it does not represent a true black body since it is narrow band. Can anything of a similar nature exist at other frequency ranges such as IR? Sorry about the rambling, but it is getting late and I am quite tired. Dave -----Original Message----- From: H Veeder <[email protected]> To: vortex-l <[email protected]> Sent: Sun, Oct 12, 2014 10:56 pm Subject: Re: [Vo]:Incandescence is the wrong color what is the other direction? (I am having hard time following the flow of thought in this particular thread) harry On Sun, Oct 12, 2014 at 10:31 PM, David Roberson <[email protected]> wrote: How does the emissivity of the alumina effect the optical appearance with regard to color? Is it possible for most of the energy to be emitted in the IR spectrum while limited at optical wavelengths? I recall looking at a piece of brightly glowing insulator in some NASA photo. The material was being held within a volunteer's hand and did not burn that person. Had the radiation been emitted at the level expected by the brightness, the person would have suffered severe burns. Could this process work in the other direction such as we seem to question in this discussion? Dave -----Original Message----- From: a.ashfield <[email protected]> To: vortex-l <[email protected]> Sent: Sun, Oct 12, 2014 4:39 pm Subject: Re: [Vo]:Incandescence is the wrong color Jed, As someone experienced with working at these kinds of temperatures in the glass industry, it was obvious that the temperature shown in the image is way below the reported operating temperature. I don't know whether this is because it was warming up, or because many consumer cameras don't show red hot things correctly. I am now somewhat dated, but I would have used a type S platinum thermocouple, at the reported temperature, for the reactor control and would have reported that reading as a useful check against the IR reading. I also wonder what they used for the heating element as that would have to be good for 1500C
