How do a mirror and a white object differ?

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Offline chris

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How do a mirror and a white object differ?
« on: 24/06/2015 19:30:46 »
A white object is reflect all wavelengths of light yet looks white, while a mirror has a "mirror" surface. Why the difference?
I never forget a face, but in your case I'll make an exception - Groucho Marx

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Offline chiralSPO

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Re: How do a mirror and a white object differ?
« Reply #1 on: 24/06/2015 21:25:41 »
Well, we have to be very careful talking about "white." Our eyes determine color based on relative intensities of red, green and blue wavelengths of light, but also in comparison to other colors observed in our field of view. (For instance, the moon is as black as asphault, but looks nearly white compared to the blackness of space)

So objects that reflect roughly equal intensities or red, green and blue wavelengths and more than their surroundings will appear white.

Mirrors are special in that they are very, very flat, and reflect all incoming light in a predictable way that maintains the relationships between incoming rays (retains an image). This is called specular reflectance. A white surface reflects light in random directs (diffuse reflectance).

Mirrors can have colors, and still maintain an image in the reflection, but modify the spectrum (color) of the reflected light.

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Offline chris

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Re: How do a mirror and a white object differ?
« Reply #2 on: 24/06/2015 22:23:21 »
Thanks; brilliant answer.
I never forget a face, but in your case I'll make an exception - Groucho Marx