Is it possible to construct a mirror such that it only reflects certain wavelengths of visible light while allowing other wavelengths of visible light to pass through? I was reading about microwave ovens and how the doors are designed to block microwaves from exiting the oven and was wondering if the same principle can be applied to visible light.


  • $\begingroup$ Would you include something like a red Christmas tree decoration, that only reflects one color, but you can still see reflections in it? The other colors are absorbed, they don't pass through, but the result is the same. $\endgroup$ – user140606 Jan 28 '17 at 0:41
  • $\begingroup$ I don't think so. The other colors need to be able to pass through. $\endgroup$ – Jake Jan 28 '17 at 0:44
  • $\begingroup$ I have. I apologize if I missed something obvious, but many results are about what color a mirror is, how filters work, etc. What I'm after is different from a filter because I don't simply want some wavelengths to be blocked; I want a range of wavelengths to be reflected (like a mirror) and the rest to pass through. $\endgroup$ – Jake Jan 28 '17 at 0:48
  • $\begingroup$ @sammygerbil is there something I missed? $\endgroup$ – Jake Jan 28 '17 at 0:52
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    $\begingroup$ "mirror reflect one color", "semi transparent mirror one color", "mirror blocks some colors." The closest thing I found was a dichroic filter, but that isn't what I'm looking for because it only allows a small portion of the spectrum to pass through while reflecting a larger portion of the spectrum. And it's see through. My bad for not specifying this if this is what I missed. $\endgroup$ – Jake Jan 28 '17 at 1:03

You could look at Optical coatings and dichroic filters.

Optical coatings are many thin layers of material of two of more different refractive indices, about one light wavelength in thickness. They structure of the coating can be designed for high reflectivity at some wavelengths and low reflectivity at others, but the switch-over cannot be too abrupt. They are very expensive to make.

Microwave oven doors work on a different principle. The holes are about 1mm diameter. Visible light passes through easily because the wavelength is very much smaller (about 0.5 microns = 0.00005cm) whereas for microwaves the wavelength is very much bigger than the holes (about 12cm). As far as the microwaves are concerned, the grille is not much different from a mirror. See How does the grid on the microwave oven window prevent microwave radiation from coming out?.

If the same principle were used for visible light, it would be difficult to get a relatively "sharp" cut-off between 2 wavelengths. But it could be done, using nano-structured materials. Fine-structuring could produce exotic optical properties. See also meta-materials.


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