In my line of work/research/slavelabor we use dichroic mirrors/lenses/filters, etc everywhere. So to quote an optics catalog: "Dichroic filters transmit light of a certain color and reflect its complementary color. They have little or no absorption. They can be used to separate a color from its complement by transmission and reflection. For color matching, they are superior to glass filters which subtract light by absorption. Dichroic filters are manufactured by vacuum deposition of thin films onto glass substrate." Remember that physics class when you talked about destructive and constructive interference? Well, that is what these jobbies work on. The dichroic film's thickness is on the order of a wavelength of light- they actually will tune the thickness to match a desired color or wavelength. All of this is for a given light incident angle, of course. So to get to Phil's question, i suppose if you wanted blue (or whatever) light in your bus, you could purchase a lightbulb that has a dichroic coating that will only transmit blue (or whatever it is tuned for). I think this is how those cheap blue head-lights work. The expensive (like those found in high end cars these days) blue-ish headlights are a whole different thing. -Matthew 84 wolfsy weekender <For more info on my reasearch, see the top link below.>
Matthew Pollard http://dynamics.chem.uidaho.edu/~dynamics Dept. of Chemistry http://www.chem.uidaho.edu University of Idaho http://www.uidaho.edu |
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