Date: Thu, 13 Oct 2005 09:19:23 -0500

Author: Paul Nord

Subject: Re: Pets, and colored light


Anodization produces a clear layer on the surface. This layer takes
dyes very well. Probably just as you said, the purple dye not only
reflects purple, but it absorbs green very well. This could be why,
as someone posted earlier this year, it is difficult to mix a purple
paint from primary colors. It's on the far end of your ability to
perceive color. Your eye needs a bit of coercing to be convinced
that it really is seeing purple.

It's interesting that your eye doesn't detect the reflection of green
(and probably the entire spectrum) from the black surface. But I
don't suppose that anything is perfectly black. Just think of it as
a very very dark grey.


On Oct 12, 2005, at 4:52 PM, Jerry DiMarco wrote:

> At 03:42 PM 10/11/2005, you wrote:
>> Thanks, yes, the purple anodizing seems to absorb (resonantly) its
>> color
>> table complement (532 nm) green.
>> That the reflection of green off purple measures less than the
>> exact same
>> (incident power, angle and surface finish) reflection off an
>> anodized black
>> surface means..? . Surface finish
>> may have
>> more an effect on reflectivity than a filter coating (anodization
>> layer).
> Yes it's necessary to know more details about the surface
> interactions. Could the anodizing process for purple result in a
> surface texture different from black? Are you measuring reflected
> light at only that frequency?
>> I guess the point was trying to make, is that there can be
>> subtraction as
>> well as addition going on, and it happens beyond just our
>> perceptions of
>> color (ie my spectrum analyzer says it's yellow, even though it is
>> just red
>> & green).
> I would expect it to register the same. Why would it be
> different?
>> Now, am into nano-particles and quantum dots, why is cabernet such
>> a rich
>> red? Could that effect be used to make giant H-alpha filters?
> Now you've left me behind. Send a postcard from Norway when
> you win the Nobel...
> Jerry
>> steve anderson, ETIII
>> SSU Physics & Astronomy Dept.
>> (ps I did an experiment and my kitty chases white light specks
>> just as well
>> as red laser dots (being careful to do it from behind, so she
>> doesn't get
>> zapped))
From Thu Oct 13 11:15:48 2005