Re: Hummingbird feeder placement - is this okay?
- From: Jerry Avins <jya@xxxxxxxx>
- Date: Fri, 26 Aug 2005 01:31:01 -0400
Lanny Chambers wrote:
... Hummingbirds are sensitive to UV, which fluorescent tape emits in quantity.
There are very few pigments that fluoresce in the UV. Fluorescence is an energy conversion process: a dye molecule absorbs a photon and later emits another, necessarily of a lower energy. (If the emission occurs a relatively long time later, we call it phosphorescence.) Photons of lower energy have longer wavelengths.
Common fluorescence is excited by UV and emits in the red or green. Fabric whiteners work best in sunlight. They emit in the blue, compensating for the yellow cast (absorption of blue) that fabric takes on with age. Remember ""bluing"?
The rare pigments that absorb light in the visible and emit at a shorter wavelength absorb two photons, not necessarily of the same color, and emit a third that is more energetic than either, but has less energy than the sum of the two.
Jerry -- Engineering is the art of making what you want from things you can get. ¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯ .
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