like the reddish glow discharge from a lithium plasma in an alumina vessel that is partially transparent to IR?
On 13 October 2014 11:43, David Roberson <[email protected]> wrote: > 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 >> >> >> >
