The Color of a Mirror: A Physics Discussion

[Hinozuki]

Okay, so I was reading a forum on the color of a mirror. End result beign that it doesn't have one. But if color is only as we percieve it, then is color not really there, and 'light' is really the only factor?

I'm just now picking up the whole physics things, so as much yet simple explanation would be appreciated.

 

[Danger]

Welcome to PF, Hinozuki.
'Colour' is just how our brains interpret various frequencies of EM radiation. A 'pure' mirror will reflect all light (of any wavelength) that impinges upon it. Like any other object, it is inherently colourless in the absence of light. When light strikes it, it re-emits the same frequency back. I would, therefore, consider it colourless at that point as well, since 'colour' as I understand it involves some absorption of the incoming light. A pure mirror has no absorption.

 

[Hinozuki]

But so then is there no such thing as color, and only light?

 

[madmike159]

Colour is a matter of prospective, people see it in different ways, but I agreewith Danger, no change in frequency makes it colourless. Black objects also have no colour, but its the oppsit because rather than reflecting everything it asorbes all colour.

 

[dst]

But so then is there no such thing as color, and only light?

Colour is not an intrinsic property of any physical object - it's a neat processing trick of our brain. The freakiest thing is that magenta is not a true "colour" in any way, shape or form, it's kinda like black/white in that sense. There is no wavelength of light to which it corresponds to.

I'd love to know how silver emerges though.

 

[Danger]

Where'd that last 'to' come from?

 

[dst]

I edited my post to swap words around and overlooked that one. I still stand by U though.

 

[Danger]

I can't figure out whether you're mocking Canuks and Brits, or highlighting the errors of Yankee spelling.

 

[pixchips]

Color and stuff from a video perspective

Hi all, I'm new to the forum ( and forums in general ) but spent most of my career on video stuff, which involves color a lot (and coloUr if you are in PAL). Anyway, as you've said, color is definitely perceptual but related to underlying physics. The same color can be derived from fairly different spectrums. Flourescent lights are a prime example: they have spikes and gaps but can end up looking white. Incandescent light spectra are more like black body radiation, broad and smooth. The same object can appear to be two different colors under each, even if the lights are adjusted (via filters or something) to look 'white'.
Imagine a 'white' object that reflects in three narrow discrete bands, one in the reds, one in the greens and one in the blues. Under light #1, a broad incandescent 'white' light, it looks white. Now imagine light #2, a 'white' light source that is made of three discrete narrow band sources. Light #2 looks white because its average spectrum has equal power in the reds, greens and blues. But if only one of #2s bands matches one of the objects reflective bands (like the red lines up with the red, but the blues and greens miss each other) the 'white' object will look red under #2. This effect makes shooting video under flourescent lights a real pain. Which doesn't explain why silver looks silver and white looks white, while both reflect the same spectra, but this is getting too long. Interesting stuff ... and all without mentioning QM.