It's actually much more complicated than that. Even clear glass absorbs all of the light that hits it. No photon actually gets all the way through a glass filter unimpeded. The photons are absorbed and remitted (in all directions) continually by all of the molecules that make up the glass. It is just by a miracle of optical physics (and very complicated mathematics!) that the re-emitted photons both constructively and destructively interfere with one another in just the right way so that the final outcome is an apparently identical bean of light exiting the sheet of glass (or filter). Look up "Extinction Theorem" in an adanced text on Optics, such as the one by Born and Wolf, if you really want the gory details. dan c. At 06:08 PM 23-10-02 +0100, Chris wrote: >The filter absorbs light of the unwanted wavelength. [snip]
