How can the radiation of gases be detected?

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Discussion Overview

The discussion centers on the detection of infrared radiation emitted by gases, exploring whether gases emit radiation similarly to solid bodies and how such emissions can be detected. The scope includes theoretical considerations, practical detection methods, and applications related to temperature sensing in gases.

Discussion Character

  • Exploratory
  • Technical explanation
  • Conceptual clarification
  • Debate/contested

Main Points Raised

  • Some participants propose that gases do emit infrared radiation, but detecting it poses challenges due to low emissivities at normal temperature and pressure conditions.
  • There is a suggestion that temperature differences in gases can be detected through the refractive index, which is density-dependent and varies with temperature.
  • One participant mentions the use of Schlieren photography as a method to visualize temperature differences in gases.
  • A later reply questions the control over the sample space, particularly regarding pressure, when sensing temperature remotely.
  • Another participant expresses interest in locating thermals, specifically warm rising air, and seeks methods to achieve this.
  • There is a suggestion to observe birds such as hawks and eagles as a practical approach to detecting thermals.

Areas of Agreement / Disagreement

Participants generally agree that gases emit infrared radiation, but there is no consensus on the most effective detection methods or the practical applications of these methods. Multiple competing views on detection techniques and their feasibility remain.

Contextual Notes

Limitations include the dependence on specific conditions such as temperature, pressure, and density, which may affect the emissivity and detectability of infrared radiation from gases.

Who May Find This Useful

Individuals interested in atmospheric science, remote sensing, or applications involving temperature detection in gases may find this discussion relevant.

Robin04
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I'm curious about that do gases emit infrared radiation the same way as solid bodies do? If yes, how can it be detected like an infrared camera does?
 
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Robin04 said:
do gases emit infrared radiation
Yes. How to detect it and distinguish it from other sources? Tough to do since emissivities are quite low at normal T and P, or density.
 
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Thank you very much. And is there another way to distinguish warmer parts of a gas?
 
You've said IR already, so I presume you're interested in sensing temperature remotely, rather than measuring it directly with conventional temperature sensors. How much control do you have over your sample space? Pressure?
 
Temperature differences can be detected via the density-dependent (and therefore temperature-dependent) refractive index. Schlieren photography does that, for example.

It would help to know more about the application you are looking for.
 
I would like to locate thermals (relatively warm, rising air) in my vicinity.
 
Look for hawks, eagles, pelicans. Refractive index: If you can find a landmark (or set of landmarks), and have some fixed pairs of points to sight over for directions of the landmarks, you can see them move up or down, left or right from day to day, or even hour to hour.
 

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