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Thread: behavior of infrared radiation

  1. #1 behavior of infrared radiation 
    Forum Freshman
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    Mar 2009
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    i want to know what materials reflect, absorb, and transmit infrared radiation. and by transmit i don't mean hot objects emitting ir, i mean an object allowing ir to pass freely through it.

    any help please


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  3. #2  
    Forum Ph.D.
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    There are many substances many are wavelength dependent though. Si,Ge,KBr,NaCl,AgCl,CsBr, Most alkali halide salts for that matter are transparent thru a lot of the IR spectrum. Polyethylene for that matter except for a few narrow bands.
    Reflectors are most metals, Au,Al, Ag are among the best .
    Absorbers: most everything else


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  4. #3 Infrared transmission and trapping 
    Forum Freshman vistotutti's Avatar
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    If you wish to trap Infrared radiation, then glass is a good starting point. its cheap and lets most of the heat of our Sun pass through.
    If you wish to keep that heat, once it has passed through the glass, then let it meet a dark surface.
    Blackend metal, rock, leaves of plants etc. will do the job.
    All these non-transparent surfaces will absorb the IR that passed through the glass, and heated them. they will then re-emit even lower frequency IR waves that (mostly) cannot exit back out through the glass, and so will be trapped.

    This is the principle that a Glass House uses, also good for Solar-Thermal electric generation and water heaters.

    I have heard that semi-silvering of the glass can enhance this effect, but have little information on this.
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    There is that which is known.That which is known to be Unknown. The unknown that is unknown to be unknown... and that which is thought to be known, but is actually unknown.
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