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A White object reflects all the visible colored light but so does a flat silver object (mirror) so what makes them look so different?

This has been answered here but that shouldn't be true because white objects can be highly polished too. Also if we make a silver object irregular/rough it doesn't turn white

EDIT:

enter image description here enter image description here

(1st img) The metal surface doesn't particularly look white (as the answer claims in the above link). (2nd img) The white surface does reflects impressions of windows here but it look nothing like a mirror (in terms of showing the natural vibrant colors of the object in front of it as a mirror does). Why the difference in nature if they do almost the same thing (i.e. reflect all the colored light. Or are we missing something?

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  • $\begingroup$ Could you provide some examples of polished white surfaces which are not reflective, and rough silver surfaces that do not turn white? That might make it clearer whether you are talking about reflectivity or color. $\endgroup$
    – Codename 47
    Commented Apr 26, 2023 at 13:20
  • $\begingroup$ @Codename47 Thanks for replying. I've added the images. I'm talking of the appearance in general. Why does the mirror looks so natural but not a white surface if they do something very similar (reflect light) $\endgroup$
    – 44yu5h
    Commented Apr 26, 2023 at 13:50
  • $\begingroup$ @SolomonSlow Yes i partly agree but if you look at the other side of the coin.. howsoever the texture of the metal is it doesn't look like white (it poorly reflects the reflection of objects in front of it) $\endgroup$
    – 44yu5h
    Commented Apr 26, 2023 at 14:32
  • $\begingroup$ Oops! Deleted my previous comment. Thought maybe it wasn't really pertinent to your question. Sorry. $\endgroup$
    – Solomon Slow
    Commented Apr 26, 2023 at 14:33
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    $\begingroup$ As an apology I offer this: engineering.mit.edu/engage/ask-an-engineer/…. $\endgroup$
    – Stevan V. Saban
    Commented Apr 26, 2023 at 15:32

2 Answers 2

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The answer in your link is correct. But you are too.

The mirror like reflection is called specular. There are degrees of smoothness. A smoother surface will have a larger specular component to its reflection. You can see this if you polish a metal surface with finer and finer grits of sandpaper. You get a mirror with 600 grit.

The two white tiles above are both smooth, but one is smoother.

A metal surface often turn grey. This is because it absorbs some of the light, more or less equally at all wavelengths. The specular reflection keeps the color of the incoming light but is dimmer. The non-specular reflection is also dimmer. If you dim a white light, it looks grey and then fades to black.

So why don't both components look grey. They would under the right circumstances. The specular component is brighter than the non-specular component, and so looks whiter. A lot of color perception happens in your eye and can work in unexpected ways. See What is Gray, from a physics POV?.

Some metals, such as copper and gold, do not absorb uniformly across the visible spectrum. They make excellent mirrors at longer wavelengths. But they do color the reflected light by absorbing shorter wavelengths.

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  • $\begingroup$ (+1) That's a pretty convincing theory. But I will wait for some more answers because i think it's more deeper than this. $\endgroup$
    – 44yu5h
    Commented Apr 26, 2023 at 14:53
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    $\begingroup$ @44yu5h Regarding the two tiles - the reflective one on the right could also have a thin coating of a mostly transparent reflective material (think clear paint (like a car clear coat), or a thin glossy film) that creates a faint mirror-like reflection, while the rest of the light that passes through gets diffusely reflected from the undersurface. The metal surface in your image has directionality to it's roughness - that is, it's anisotropic, which is why you get these bright and dark bands (it stretches the reflected image perpendicular to the streaks). $\endgroup$
    – Filip Milovanović
    Commented Apr 29, 2023 at 12:41
  • $\begingroup$ @44yu5h BTW, the answer you linked to in your question doesn't explain as much why an object is white, but rather why an object that is white (or any other color, for that matter) doesn't appear mirror-like. It's because of diffuse reflection (light being scattered in all directions) - this could be caused by microscopic irregularities of the surface itself, or by other mechanisms like subsurface scattering, or a combination of both: see this Wikipedia article. $\endgroup$
    – Filip Milovanović
    Commented Apr 29, 2023 at 12:53
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    $\begingroup$ Thin film coatings can definitely affect reflectivity. They are used for mirror coatings, antireflection coatings, and much more. But to make a mirror, you have to have a smooth substrate, and the thickness of the coating has to be carefully controlled. For more information, see Dielectric Coatings $\endgroup$
    – mmesser314
    Commented Apr 29, 2023 at 14:03
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    $\begingroup$ @44yu5h But you're right that in general there's more to it when it comes to how this diffuse scattering in all directions comes about - most of the time (depending on the material) it happens because of internal structure beneath the surface (subsurface scattering). Read the "Mechanism" section in the Wikipedia article I liked to, it discusses exactly what you want to know. 2/2 $\endgroup$
    – Filip Milovanović
    Commented Apr 29, 2023 at 14:47
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The metallic surface is an electrical conductor while the white surface is a dielectric. These reflect light differently because a dipole response is induced in the dielectric. There's a lot more to be said about the physics, but that should be enough information to get you started down the rabbit hole.

As a sidenote, 3M does produce a dielectric material that reflects light like a mirror and with extremely high efficiency. However, it accomplishes this by structuring the dielectric in very precise, thin layers to achieve an effect that would not be possible using a bulk isotropic dielectric.

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