How Do We See Color?

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! good home for the where them


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