Re: ATM CD Prism

[astillma@nit.AirTouch.COM (Anthony Stillman)]

The color of sound

You wrote:
After reading the message re: putting the CD in a micro wave, I happened
to have on at hand.  I held it up and was using it as a mirror
reflecting a 100 watt light bulb overhead.  I noticed across the surface
on both sides a perfect rainbow from violet to red.  Can some of you
optical guys tell me where the prism effect comes from.


Diffraction, as in diffraction grating.  When a regular pattern reflects light certain 
wavelengths of light will interfere with its self.  Hence, some colors are made brighter 
and some dimmer.  This is a function of angle, that is path length is a funcition of 
angle.  When the pattern is small enough the effect becomes quite visible.  You can also 
see the effect by holding a record (you know vinyl, 33 and a third ) at a slight angle 
toward a light and looking at the reflection.  Also the grains in magnetic tape are 
regularly enough that some time you can see sort of a speckly color in the reflection 
from a very bright light.

Perhaps all of this means that music and the rainbow are some how linked in some sort of 
cosmicly meta-physical wu wu way.  Naaaaaaa...

Anthony