There are many ways that we use color. Artists use different colors to express
emotions.
Marketers attach color to their brands to make them more recognizable.
Animals use colors to ward off predators
or attract mates-- and people do, too. What is color?
Scientists define color at the limited range of light that we humans can see.
We classify different types of light based on their wavelength,
which can be anywhere from many meters in between each wave
peak to lengths as short as the diameter of an atom.
The full electromagnetic spectrum
ranges from high-energy light waves with short wavelengths like cosmic and gamma rays
to low energy light waves with long wavelengths
like radio waves. The light we are able to see, called the
visible light spectrum, ranges from violet light,
which has a wavelength of about 400 nanometers, to red light,
which has a longer wavelength about 650 to 700 nanometers.
But how do we perceive the visible light spectrum?
When light bounces off an object, like this
painting, into our eyes, it first hits the cornea,
a film that lays on top of our eyes. This layer
bends light towards the pupil, which dilates or contracts to let in more or
less light.
Once light passes through the pupil, it is sent to the lens,
which angles and focuses the light to a point on the outer layer of the retina.
Here, light-sensitive cells
called rods and cones send information to ganglion nerve cells in the inner retina.
Ganglion cells then send the information to the optic nerve,
which sends the signal to the brain, where the signal is processed and
interpreted.
Rods and cones, the two types of light sensitive cells
located on the outer retina, have different jobs.
Rods are responsible for our perception of light and dark
and our peripheral vision. Cones are what allow us to see color.
They are found in the center of the retina, where light is
focused. Cones come in three varieties,
each sensitive to a different light. Interestingly,
we have more cones sensitive to red light, meaning our vision is best for warmer
colors like
reds, oranges and yellows.
However, our cones aren't sensitive to light with wavelengths shorter
than 400 nanometers or longer than around 700 nanometers.
For example, a gamma wave's wavelength
is about the size of an atomic nuclei,
which is much too short for any of our three types of cones to sense
Radio waves are too long, with wavelengths
longer than two Empire State buildings put together. That doesn't mean that these
forms of light
aren't visible, per se. Other animals
have different kinds and number of cones, which allows them to see the world
differently than we do.
Dogs, for example, are more limited in the wavelengths
they can see because they only have two types of cones,
leaving them "colorblind" to differences between red and green.
Butterflies have four types of cones in their eyes,
letting them see ultraviolet light.
The animal with the best color vision might be the mantis shrimp,
which has 12 different kinds of cones.
If Pablo Picasso and Paul Klee
created amazing works of art with just three types of cones,
imagine the masterpiece the mantis shrimp would create with 12!
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