Black and White and Colors
Is it true that black is an absence of color
(technically NOT a color)
and white is a combination of all colors?
(Your answer will help my debate with my wife....)
Our eyes react to different shades of light, and what we determine as colors
are different wavelengths of light. When we say an object is a certain
color, it is because it is reflecting more of a certain wavelength light.
For example red objects reflect "red" light, or light with a longer
wavelength (lower frequency) better than other types of light.
So, we determine the color by the primary type of light the object reflects
(or emits if it is a light).
We also perceive other properties of colors, and that is lightness or
darkness. A light colored object may reflect one color especially well, but
also reflect other colors as well. A very light green object, for example,
reflects green very well, but also reflects most other colors, just not as
Dark objects tend not to reflect light very well at all, even if it reflects
one color better than the other.
White objects, tend to reflect all types of light equally well, and tend to
reflect most of the light cast on it.
Black objects also, tend to reflect all types of light equally, they just
dont reflect much of the light cast on them.
In computer graphics, we use combinations of just three lights to produce
the colors on a screen, red, green, and blue. We also use different systems
for calculating colors. One of those is hue, saturation, and lightness.
This system is more accurate in describing how we perceive colors. The hue
is what we call color--red, brown, white, etc. The saturation is how much
of the other colors is present, and the lightness is how bright the color
The interesting thing about this system is, white and black have the same
hue and saturation, the lightness is all that is different.
Anyway, what all this boils down to, is the answer to your question simply
depends on how you look at the problem.
On one level, you are right. Black doesn't reflect light, and white
reflects all colors. On the other hand, if you are talking to someone like
me who deals with generating colors on a computer screen, black and white
are exactly the same color, one is just brighter than the other.
I hope this helps your discussion.
Well, I think color is best defined as a human sensation. That is,
we should define color as that property of visual impression which
evokes the word ``red'' when looking at the setting sun and ``blue''
when looking at the daytime sky. From that point of view, white and
black are both single, real colors, no less than red or blue or
You may be thinking of defining color in terms of the frequency of
the electromagnetic radiation involved, i.e. green light is that of
wavelength 5000 angstroms, red light is that of 7000 angstroms
wavelength, and so forth. Part of the problem with this definition is
that the human eye does not simply analyze the frequencies of incoming
light when it perceives color. There are far too few visual pigments
for that. Hence the color we perceive does not always correspond to
the color of the light received.
For example, an object will be perceived as yellow if it reflects
primarily yellow light, BUT ALSO if it reflects not one photon of
yellow light but reflects red and green light equally. Furthermore,
most people would want to call this object yellow, suggesting the key
defining question for color is: how does the eye perceive it?
We run into problems with your definitions of black and white if we
try to define color as frequency, also. A certain object may reflect
quite strongly in the infrared or ultraviolet, outside the range of
human vision, but not at all in the visible. Such an object hardly
meets the criterion of reflecting no light of any color, yet it would
*look* black, and be called black by any ordinary person looking at
it. By the same token, an object could reflect radiation equally
across the visible spectrum, and yet have a very complicated
dependence on color of its reflectance outside this narrow region.
Such an object would *look* and be called white, but does not meet
your criterion of reflecting radiation equally at all frequencies
We cannot even standardize the ``visible'' region. Not all living
creatures see in the same color range we do. Spiders see into the
infrared and bees into the ultraviolet, and so there are objects that
look black to us which are NOT black to spiders, and objects that look
white to us that are NOT white to bees. Individual human beings
presumably also have some variation in how far up and down in color
they can see, just as there is variation in how high and low you can
So I think it is futile to try to match the usual, everyday sense
of the word color to anything other than the human sensation in the
eye. And by this token black and white share equal status with red
Let me also mention that a black object has a few definitions, some
of which may surprise you. A black hole, for example, is an object
that emits no radiation whatsoever. This is close to your meaning, I
think. But on the other hand, a black body is one which emits and
absorbs radiation of all frequencies equally well. The Sun, for
example, is a black body. A rather white and glowing black body, it
Red (interesting name considering your question!),
We call an object 'black' if visible light hitting its surface is not
reflected...that is, the light is absorbed by the object and our eyes do not
see a color reflected from the surface. We see a plant as green because the
plant absorbs wavelengths of visible light including all but green, which
is reflected back and is what we see. The same goes for all other colors.
Since we have defined 'color' as the wavelength(s) of visible light
reflected from an object, with the remainder being absorbed, a black object
has no 'color' by our definition. An object we call 'white' reflects all
wavelengths of visible light and therefore could be considered all-colored.
Good luck in your upcoming debate. :)
Thanks for using NEWTON!
Richard R. Rupnik
Internal Quality Auditor
White light contains light of all frequencies. In that sense, white is a
combination of all colors. Black objects absorb light of all frequencies.
This means that very little light is reflected from them. Black is the
absence of light.
As far as the absence of color is concerned... you know that if you combine
pigments or dyes of different colors, you don't end up with white. Dyes
and pigments work by absorbing light in certain frequency ranges, and
transmitting or reflecting light of other frequencies. If two different
dyes are combined, the mixture absorbs light characteristic of BOTH dyes,
and transmits light of the remaining frequencies. If you mix togtether
dyes that are truly complementary, the mixture will absorb light of all
frequencies, and thus be black. (In practice the best you can do is get a
muddy brown, because the different dyes are only approximately
complementary.) So it depends on what you mean by "absence of color."
We perceive colors because we have three types of "cone" cells in our
retinas, each of which is most sensitive to certain frequency ranges.
These ranges correspond pretty much to red, green, and blue. Our brain
interprets the different intensities of the signals from each type of cone
cell to decide what color it sees.
Richard E. Barrans Jr.
Light travels in waves and is made up of all of the colors of the spectrum.
You can see this when light is bent through the use of a prism. When light
hits an object 3 things can happen: it can be absorbed, it can be reflected
or it can be transmitted (or shine right through). When white light hits an
object, usually some of the light's energy is absorbed by the object. Any
part of the spectrum (energy) that is not used by the object is reflected
back. The portion of the spectrum that is reflected back is the color that
you actually see. For example, the reason that green plants are green is
that chlorophyll absorbs light in the blue and red and reflects light in the
green and yellow. So black is actually when all the light energy is absorbed
and no light is being reflected back. So it isn't really the absence of
color, its the absence of any reflected light. White is actually when all
of the light is reflected and none of it is absorbed. So it is still made up
of all of the colors of the spectrum.
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Update: June 2012