Looking out of the window at night from a lit room, you see yourself reflected in the window and, depending on the lightness or darkness outside, you also see things outside. We can say:

Some light from the inside is reflected and some light from the outside comes in.

Is it physically (and technically) possible to have a "window" screen for which the the two 'some' in the sentence above can be changed to 'all', as in the diagram?

enter image description here

  • Light from the left passes through 100%, independent of angle.
  • Light from the right is reflected 100%, independent of angle.

I wonder if this is possible and if yes, if there exist technical solutions, or whether some physical principle prevents this?

  • $\begingroup$ I don't suppose that a video camera & screen counts as a valid technical solution? ;) $\endgroup$
    – PM 2Ring
    Commented May 1, 2020 at 14:09
  • $\begingroup$ Nice workaround:-) But no, I'd rather learn about some "passive" device (with the suitable definition of passive). $\endgroup$
    – Harald
    Commented May 1, 2020 at 14:14
  • 4
    $\begingroup$ Time reversal symmetry generally prevents it. Now, for a polarized beam one gets some of the way with a polarizer and Faraday rotator, which happens because the Faraday rotation is not symmetric. $\endgroup$
    – Jon Custer
    Commented May 1, 2020 at 14:18
  • $\begingroup$ I wonder if an anti-glare coating on the left but not the right would work. Not 100%, clearly $\endgroup$
    – Dale
    Commented May 1, 2020 at 14:18
  • $\begingroup$ @PM2Ring - dupe found... $\endgroup$
    – Jon Custer
    Commented May 1, 2020 at 14:22


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