What's the difference between a mirror and white?

[neiroatopelcc]

Hello. Was asked by a collegue about mirrors and white.
Was some offtopic after talking html color codes and why white is 'all colors' since it isn't if you mix all available colors on a paint brush (reallife thing ; would turn to some sort of brown).
So I explained about wavelength and that being why black is the absense of reflection and white is all visible light reflected.

After explaining that he asked why a mirror isn't looking white then - since it reflects all. A brilliant question really. A question to which I have no answer.

Does anyone else?

 

[Kari]

reflection vs. scattering?

http://en.wikipedia.org/wiki/Reflection_(physics)
http://en.wikipedia.org/wiki/Scattering

 

[elel]

Karl's right. When you look at a black shiny object you can see reflections in it, even though the material it's made out of is black. Mirrors are actually silver in color, they just reflect the light that is sent to them instead of changing it.

 

[will_chellam]

The main difference like the posters above said is coherence - basically a mirrored surface is very smooth, at a molecular level, so that coherent beams of light are reflected back off in an organised manner.

White surfaces are rough at a molecular level and therefore a coherent beam of light scatters back randomly therefore destroying the reflected image.

 

[will_chellam]

This reminds me of a question I heard once, which was how do projectors project black onto a white screen?

 

[elel]

The answer is that white looks black next to the bright projected colors. So the white screen is used for the black.