Re: how do you make WHITE?

[brian whatcott <inet@INTELLISYS.NET>]

At 22:51 3/6/99 -0500, John Denker wrote:
> At 05:21 PM 3/6/99 -0500, Donald wrote:
> > Why can the transmission of light (intensity) be greater through
> > oil-soaked paper than through the same paper dry?
> ... If the
> locations are exact, but the scattering parameters (e.g. size) is variable
> from site to site, then we get Mott localization.  If the sizes are uniform
> but the locations are randomized, we get Anderson localization.
> Note that you cannot make paper (or paint) that is really thin and really
> white.

> Oil permeates the pores of the paper and *index matches* to the cellulose.
> We no longer have a random array of index-changes.  We a thin sheet of
> relatively uniform index, and the light just waltzes through.
>
> You don't get perfect transparency for various reasons:  (1) Typical oil
> isn't a perfect match for cellulose.  (2) Typical paper contains not just
> cellulose but other junk.  If you match to one, you can't match to the
> other. (3) What's worse is that the cellulose fibers are *hollow* and
> you'll never get oil into the cores.  Therefore there will always be some
> scattering off the cores.  If we could lay hands on some paper made of
> randomly-arranged solid fibers (such as rayon, which is solid cellulose), I
> predict the oil-spot effect would be really spectacular.
>
> One final remark: ... A large-gap semiconductor should be called
> merely a semi-non-conductor, since it cannot be used as a practical
> insulator.  It will not immobilize any charge injected onto or into it.  To
> do that, you need localization of the electron wavefunction.
>
> Cheers --- jsd
This was a truly splendid offering. It offered insight.
It offered experimentally verifiable prediction.
It was great!

 That's what makes it such fun to nit-pick.   :-)

The problem lies in the last sentence. It's a physicist's sentence.
John believes he is talking about a physical mechanism which can
provide a force field environment which holds charged particles in
place.
 But what he actually SAYS, is a methematical construct.
"To immobilize a charge, you need localization of the electron
wavefunction."

John is certainly not alone in this way of writing.

Brian
brian whatcott <inet@intellisys.net>
Altus OK