I Does plain glass reflect infrared radiation?

  • Thread starter charles65
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Glasshouses warm because supposedly heat (infrared) is trapped inside. However I am looking for a description of the process. Is it by glass reflecting infrared back into the glasshouse, or is it by glass absorbing infrared, heating up itself and then warming the glass house interior by back-radiation?

These look like two different processes.
 

jim mcnamara

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Window is essentially transparent to visible light, but reflects infared wavelengths, this results in trapping(reflecting) re-radiated heat inside the greenhouse.
 
Another point is that Infrared is from typically 700nm to 1mm is much broader than Visible light (400nm to 700nm). Because of that Infrared properties vary a lot with different materials. Many materials transmit NIR just like visible light where as opaque to higher wavelengths.

Found the following interesting IR and visible properties of material.
https://www.edmundoptics.com/resources/application-notes/optics/optical-glass/
https://www.edmundoptics.com/contentassets/639fec6d719643a8a3400e1205e6fa84/fig-4-cmi.gif
 

berkeman

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And another piece of evidence that glass reflects IR...

The shower in our master bathroom uses clear safety glass. We have a passive IR (PIR) sensor that turns on a nightlight in the bathroom, and it times out and turns off after 5 minutes. When I open the glass door and get out of the shower, the PIR sensor turns on the night light... :smile:
 

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