Although mirrors should in theory take the color of the objects they are reflecting, many of us would recognize their color as silver. Do mirrors have a real color? Or are they colorless? To answer this question, we picked out the best explanations from the internet.
Not all mirrors are perfectly reflective, and things can be done to a mirror to make it less reflective (like fogging, smudging, etc.)
If you look at something like the side of a butter knife, you can see that it has a color, despite also reflecting the world around it. If you polish the side of that knife enough, eventually you’d get a usable mirror.
Common household mirrors are a thin layout of silver on the back of a pane of glass, so their color when less than perfectly reflective is the same as the color of unpolished silver.
More: as had been pointed out, modern mirrors use aluminum, since it is almost as good but a lot cheaper. Still, the language evolved in a time when aluminum was less common.
Mirrors are usually pieces of glass with a metallic layer painted on (a multi-step process to produce a well bonded shiny metal layer. For most mirrors, this metal layer is silver or aluminium.
So now the question is: why does silver (or aluminium) appear grey/silver in colour? Or more broadly speaking, what determines the colour of reflective metals?
Metals have what is known as a plasma frequency. In simple terms, this frequency is the upper limit for electromagnetic radiation that the electrons in the metals can respond to. Frequencies higher will simply pass through and frequencies lower will be reflected. Basically, the electrons can’t ‘keep up’ to the high frequency vibrations and don’t respond. When the electrons can ‘keep up’ (for EM waves with a frequency lower than the plasma frequency), they vibrate and re-emit that radiation. This is the reflected light we see.
For most metals, like silver and aluminium, this frequency is in the ultraviolet region. This means that all lower frequencies, such as the entire visible light range, are reflected. The result is a shiny white, silver.
For other metals, say copper, this plasma frequency is lower, closer to red in the visible light range of EM waves. This gives the reddish-brown colour of copper.
You can see your reflection in a shiny car, right?
How about the TV screen when it’s off? We can recognize the colors of those items, even though they are reflective, and mirrors are no different. Reflective surfaces can be any color. Mirrors are simply a neutral color that better reproduce the colors one would see if looking directly at the object.
Silver is technically not a color. It’s just a “reflecting gray” if you want to call it something. In your mind the mirror is colorless with a “reflective” attribute; means that, by itself, the mirror only has brightness but no color. That darkness-to-light spectrum you perceive on the mirror somehow translates as a white-to-black spectrum to your brain. A white to black spectrum is basically an array of grays. Grays with reflection. That gives you a silver-ish perception
You have to be careful when using the word “color”. We mean many different things by that word. When you get specific, silver is not a color by many definitions. For example, there is no silver wavelength of light and in terms of pigmentation mixing, there is no silver pigment.
Instead, silver is a color in the same sense that matte black is a color and in order to understand that, you have to understand that there are three components to reflected light:
- Wavelength (e.g. blue)
- Attenuation or albedo (how much is reflected, e.g. 20%)
- Scattering (e.g. matte vs gloss surfaces)
By “silver” what we really mean is that no particular wavelength is suppressed (the reflection’s color doesn’t change), the albedo is relatively high (e.g. it is not seen as a “black” surface) and there is little scattering.
Change the wavelength, and we would call it something like “metallic blue” or just “blue”. Change the albedo and you might call it “black”. Change the scattering and you might call it “gray” or “gunmetal”.
Mirrors actually tend to have a slightly green tinge to them. It’s not noticeable if you’re just looking in one but if you have two mirrors facing each other and look into the infinite reflections it gradually tunes more and more green