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Magic Mirror on the Wall, How Do You Even Work at All?

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Max The Magnificent
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Re: Inquiring minds ...
Max The Magnificent   12/2/2014 6:32:02 PM
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@some guy: ...even after you rotate it from portrait to landscape?

ROFLOL

Some Guy
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Re: Inquiring minds ...
Some Guy   12/2/2014 6:18:56 PM
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@mhrakin

"... all in your head!"

I've suspected this for some time now. And my kids will tell you they knew it all along.

mhrackin
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Re: Inquiring minds ...
mhrackin   12/2/2014 5:22:54 PM
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@some guy: The answer was already given in an earlier post: it's basically all in your head! Try it lying down....

ccorbj
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Re: Still Confused
ccorbj   12/2/2014 4:58:54 PM
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@GSKrasle - love it! Welcome to our mutual descent into madness. One of the things a photon can couple to is a plasmon, an excitation in the electron gas in a metal. Thanks for the added detail. All this goes to shows, the deeper you dig, the more confused you are going to get.

And then there's the measurement problem, which is only for advanced insanity...

Some Guy
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Inquiring minds ...
Some Guy   12/2/2014 4:36:53 PM
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... just want to know:

Why does a mirror swap left and right,

but not up and down?

 

even after you rotate it from portrait to landscape?

Max The Magnificent
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Re: Still Confused
Max The Magnificent   12/2/2014 3:47:20 PM
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@GSKrasle: ...and then it starts to get complicated and confusing...

I'm laughing through my tears :-)

GSKrasle
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Re: Still Confused
GSKrasle   12/2/2014 3:34:22 PM
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Max,

 

It gets worser! 

Back in my MatSci/Metallurgy days, I did a big research project on why metals are, well, metallic. In particular, why Cu and Au are coloured, and the chemically/electronically very similar Ag is not. 

There are a lot of presumably equivalent models that apply to light/EM reflection (and transmission), some particularly applicable to metals, some to anything metallic-looking, and some that are more general. Modeling metals as a conductive 'gas' of electrons with a periodic (or for liquids, a statistically-distributed) lattice of positive charges works, and gives a 'plasma temperature' for the 'gas' which is very high and an amusing thing to contemplate. Impinging EM fields induce currents, which can (depending on the local resistance, inductance, capacitance [which are affected by the relativistically-adjusted electron{/hole} mass and the positive lattice]), produce a new outgoing EM field with, you guessed it, the characteristics we expect in a metallic reflection. But that model is inapplicable to non-metals, where reflections also have a peculiar dependency on the polarization of the incident EM field. But for metals, this model makes light reflection similar to antenna reflection. Modeling the surface as a mismatch in the complex electromagnetic impedance works too (and was the most successful for my purposes). (The complex refractive index is a function of λ, ε, μ, and all sorts of other parameters.)

Long story short, Ag IS coloured... if you're an insect. Cu, Ag and Au basically have a low-pass in their reflection characteristics, as does everything, but Cu is in the green, Au in the blue, and Ag in the near-UV. On a larger-scale than the narrow window of human visual sensitivity, they look very very similar. Li also has interesting characteristics, and both the colours of the transmitted light (if you have a thin enough layer) and of the liquid metals are interesting. A practical consequence is that UV and a UV-sensitive camera can be used to distinguish Ag- from Al-plated chips (which was once important to me when some dice got mixed and had to be non-contaminatedly segregated).

Oh, and your concern about 'bumpiness' of the surface applies only if that 'bumpiness' is comparable-to or larger than the incident wavelength (and THAT may depend on incident angle)....

Which brings me to my image-processing/software days: When rendering an image, the brightness of the light from a point on a surface varies according to how close (angularly) the eye is to the perfect specular direction. For matte objects, that specular reflection brightness may be modeled as proportional to (cos(θ)), where θ is the angle from the viewing direction to the ideal specular direction. For shinier objects, there is an exponent: (cos(θ))^n, with n=>∞ for metallic reflection. (Phong Shading in Raytracing). So 'reflections' from your bumpy surfaces will actually have an exponent n which is a function of λ, just as the components of the complex index of refraction (n, κ) are.

And then it starts to get complicated and confusing; I doubt this site would be happy if I dumped a bunch of equations on it.... 

Max The Magnificent
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Re: The magic of mirrors
Max The Magnificent   12/2/2014 2:24:33 PM
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@RichQ: I'd prefer port and brandy.

I'll drink to that! LOL

RichQ
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Re: The magic of mirrors
RichQ   12/2/2014 2:22:40 PM
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I'd perfer port and brandy.

Max The Magnificent
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Re: The magic of mirrors
Max The Magnificent   12/2/2014 2:06:48 PM
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@RicjQ" It seems to me that the problem is our use of the terms "left" and "right" which are relative to the observer.

You'd prefer "Port" and "Starboard"?

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