"Rich Webb" wrote in message
...
On Sun, 25 Sep 2011 10:20:24 -0700, Jeff Liebermann
wrote:

On Sun, 25 Sep 2011 17:54:07 +0100, "Arfa Daily"
wrote:

Anyway, enough time spent on this now. Been enjoyable.
Arfa

Humor me for a moment. Take a digital camera photo of your favorite
CFL lamp. Turn off all the other sources of light. What color do you
get? Here's mine:
http://802.11junk.com/jeffl/crud/FEIT-23w.jpg
See a problem perhaps?

Extra credit. Find various sheets of blank paper with an assortment
of brightness from about 85 to 105. Photograph those using either a
CFL lamp and an incandescent lamp source. What colors do you get?
(Note that the 105 brightness contains phosphors resulting in the
reflected light actually being brighter than the incident light).

You might want to buy a cheap LED UV flashlight and a diffraction
grating, for more fun with lighting.
http://www.scientificsonline.com/holographic-diffraction-grating-film-10036.html

Or, from the same source (as well as Amazon, etc.) this thing
http://www.scientificsonline.com/precision-economy-spectrometer.html
which includes a nm scale. Some examples of what it shows at
http://home.comcast.net/~mcculloch-brown/astro/spectrostar.html

--
Rich Webb Norfolk, VA

Some interesting findings there. Today, this dropped into my email

http://www.ledlighting-eetimes.com/e...s_id=222907475

Looks as though it might address some of the points I made, particularly in
regard to the (typically) non-omnidirectional light from a LED lamp. I had
long wondered why the cooling core for the LEDs was not made spherical, so
that the light would be omni.

Arfa