[LRflex] Re: Was a bunch of stuff, black fabric

Take a look at some physics sites about black body radiation - there are 
quite a few interesting things about what frequencies/wavelengths are 
actually absorbed and what is reflected (there may very probably even be 
a colour temperature factor in there somewhere too) - Too many pages to 
give actual links, and enough reading for a week.
Douglas

William Abbott wrote:
> To all seekers of truth:
>
> See
>
> http://www.straightdope.com/mailbag/mblackcool.html
>
> http://www.newton.dep.anl.gov/askasci/gen01/gen01173.htm
>
> All the best,
>
> Bill
>
>
> On Nov 26, 2006, at 7:06 PM, Aram Langhans wrote:
>
>   
>> OK David.  I am ready to tackle the black fabric question. Still  
>> about 30
>> message behind, though.
>>
>> I guess I really don't have an answer, or a guess like Colin, but I  
>> do have
>> a few thoughts.  The IR can only come from two sources.
>> 1)  Light is being absorbed by the dark pigments and degraded to  
>> heat and
>> re-radiated.  This is happening in both non-synthetic and synthetic
>> materials.
>> 2)  Ambient IR is being reflected from the surfaces.  I assume this  
>> is also
>> happening to some extent from both fabrics.
>>
>> So, how to figure out what is going on.  I could suggest two possible
>> experiments.
>>
>> 1.  Find some synthetic and non-synthetic black material that when
>> photographed with film or read with a light meter give the same black
>> readings.  They absorb the same amount of visible light.  Now  
>> photograph
>> them in a very cold room (walk in freezer or outside on a day like  
>> today)
>> and see what the results are.  Maybe synthetics re-radiate at a  
>> different
>> wavelength than non-synthetics?
>>
>> 2.  Using an IR flash, photograph them in total darkness to see if  
>> there is
>> any difference in what they reflect.  Maybe synthetics reflect more  
>> IR than
>> non-synthetics.
>>
>> I do not think there is any reason to believe that just because an  
>> object is
>> black it behaves the same as far as absorbing or reflecting in the  
>> IR range.
>>   Some materials may be very good at absorbing visible and IR, and  
>> others
>> only visible.
>>
>> I don't have an IR flash nor do I have an M8 to try these.  Also
>>
>>
>>     
>
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