Re: how do you make WHITE?

[Ludwik Kowalski <KowalskiL@MAIL.MONTCLAIR.EDU>]

"John S. Denker" wrote:

> Let's start with something that isn't white.  A piece of quartz is highly
> transparent.  It does not absorb light.  It does have an index of
> refraction.   A light beam will partially reflect off the air/quartz
> interface due to the index mismatch. If you take a zillion identical small
> quartz spheres and arrange them in a regular lattice like a crystal, you
> might think that all those little reflections would add up to make
> something quite non-transparent, but in fact a funny thing happens.  If the
> lattice really is perfect, the scattering is coherent.  The coherent
> forward scattering reconstructs the incoming wave perfectly, making the
> lattice transparent (although it has a refractive index of its own).  You
> can visualize this in terms of the Huygens construction if you want.

> For more on this see _The Feynman Lectures on Physics_ volume III

> chapter 13,
> or any solid-state physics text.

How large is the radius of each quartz sphere? My prediction is that
spheres whose radia are 1 mm, for example, will not "reconstructs
the incoming wave perfectly". Are you referring to a real experiment
or to gedankening?

Feynman is discussing the one-dimensional lattice of atoms, not a
three-dimensional collection of macroscopic spheres.

Ludwik Kowalski