[TheForge] plastic forge? OT:

[Bruce Freeman]

Free electrons are involved in the absorption of light due to the fact
that a photon of light will "promote" an electron from a lower- to a
higher-energy state.  In pure elements, this is what gives rise to the
absorbance spectra of the element (hydrogen, for example).  It is also
the case for molecules.  The more possible energy states available for
an electron to "reside" in, the more different possible transitions
possible.  A photon of a particular energy corresponds to a 'color'.

I don't see how running a current through a transparent material would
have anything to do with color.  Salt water conducting electricity
remains clear, but then electrons don't run through salt water -- ions
do.  I would suppose it unusual for a transparent material to be able
to conduct electricity.  Can you think of one?

On Thu, Jun 16, 2011 at 12:38 PM, peter fels <artgawk at thegrid.net> wrote:
>
>>
>>
>>
>> As you probably know, diamond is crystalline carbon, in which each
>> atom is connected to four others in a tetrahedral configuration (i.e.,
>> the OTHER four carbons are at the corners of a tetrahedron).  Very
>> strong, very hard, no free electrons so completely transparent.
>>
>> By contrast, graphite is crystalline carbon, in which each atom is
>> connected to only three others in a hexagonal array (i.e., honeycomb
>> or chickenwire shape).  This is even stronger than diamond within the
>> plane.  However, the myriad of layers of carbon are only held together
>> by their electronic interaction and whatever stuff that attracts to
>> between the planes.  There are LOTS of loose electrons floating
>> around, so virtually any wavelength of visible light can be absorbed,
>> rendering the stuff black.
>>
>>>>> How fascinating.
> Bruce, do you know why free electrons absorb light?
> Does this mean that running a small current through or across a transparent  material will male it opaque?
>>>>>
>>>>>>
>>>>>>
>
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-- 
Bruce
NJ