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The difference between a white object and a mirror is mainly scattering versus reflection. If we neglect this difference and define the reflectivity by input energy minus transmitted energy minus absorbed energy, what is the material with the highest reflectivity? With material, I mean something like a single element mirror, any multi-layer mix in a dielectric mirror or any sort of white-colored surface.

As the reflectivity depends on the wavelength, let's assume, our input energy is distributed according to the sun's spectrum (on the earth's ground). Let's further assume, there is no polarization. With these definitions, it should be possible to define a reflection coefficient as a scalar.

I am interested in theoretical aspects of the problem, laboratory results/examples and home-made solutions (alumium foil, wall color, etc)

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  • $\begingroup$ It isn't clear what you're asking. Are you asking for the best known reflector of light with the solar spectrum? $\endgroup$
    – John Rennie
    Commented Jul 26, 2014 at 9:31
  • $\begingroup$ @JohnRennie essentially yes, I am asking for the best known reflector as defined in the question. But as mentioned, I would also be grateful for some theoretical explanatations, and the performance of the best white and best mirroring material $\endgroup$
    – Patrick Häcker
    Commented Jul 26, 2014 at 10:23
  • $\begingroup$ That's a big question because absorption is determined by the band structure of the solid and also its defect states, while reflectivity is determined by the refractive index, which is in turn determined by the electronic structure. You're asking us to write you a several thousand word essay. $\endgroup$
    – John Rennie
    Commented Jul 26, 2014 at 10:28
  • $\begingroup$ @JohnRennie: That's not my intention, sorry for being unprecise. I think the level of detail is important here. You already answered my question to some extent without needing several thousand words (thanks for that). Although I am new to physics.stackexchange, I think it's ok for stackexchange in general to give a high-level answer and optionally provide links for more details. But as I didn't found the links myself, I was asking the question here. I haven't read physical journals regarding this topic, though, as I usually deal with lower frequencies. $\endgroup$
    – Patrick Häcker
    Commented Jul 26, 2014 at 10:39
  • $\begingroup$ @JohnRennie: Regarding the physics in your comment: Isn't the band structure of the solid also determined by the electron structure? So doesn't absorption and reflectivity follow from the same root cause (electrons)? If that were true, I think one could reformulate my question into: What material should you take to have optimally arranged electrons for reflection? $\endgroup$
    – Patrick Häcker
    Commented Jul 26, 2014 at 10:42

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