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Comparative absorption rates

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ocalhoun
Okay, here's a very specific question, but I can't find the answer anywhere (although there should be one somewhere).

How much energy is absorbed by glass when light is passed through it (resulting in heat) compared to when electricity passes through wires (also creating a little heat)?

If you can find the answer to this at all, I'd like to know how much all of these absorb:
Light through air
Light through water
Light through ordinary glass
Light through crystal (ultra-pure glass)
Light through crystal (such as quartz or other mineral)
Electricity through copper
Electricity through silicon

fohsofrlkesfsle

Last edited by ocalhoun on Tue Jan 16, 2007 10:44 pm; edited 1 time in total
peaceninja
i had a similar thought the other day while reading an article on solar panels. It'd be interesting to see how much energy/heat/light is absorbed while going through a two-way mirror as well.

regardless the answer probably lies to some 'absorption index' or some other physics jargon that you otherwise don't know what to search for unless you knew the name of the concept.
Bikerman
ocalhoun wrote:
Okay, here's a very specific question, but I can't find the answer anywhere (although there should be one somewhere).

How much energy is absorbed by glass when light is passed through it (resulting in heat) compared to when electricity passes through wires (also creating a little heat)?

I used to manage the computer systems at Corning Optical Fibres so I know a bit about this simply from talking to the engineers at the plant.
The loss (attenuation) in optical fibres is measured in dB (Decibels). The mode of attenuation depends on the type of fibre. Multi-mode fibre has a larger internal core size and thus light can travel in various paths (modes) down the fibre. Single mode has a much finer core and light can only travel down the core in 1 mode. It is important to note that signal loss is due to a combination of attenuation and 'signal smearing' which describes the single pulse of light spreading out either due to interference or due to chromatic spreading (different frequencies travel at different rates down the fibre).
Single mode fibre will show attenuation of around 0.5dB per km.

Here's an article going into more detail
http://camres.frih.net/resources/IT/OF-attenuation.pdf

Hope this helps

Regards
Chris
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