The Visible Spectrum: Overview With Colors Listed in Order of Increasing Wavelength

Visible light spectrum color scale with wavelengths in nanometer

At first glance color and advanced math seem to be miles apart from each other. We associate color with abstract beauty and subjectivity. Meanwhile math is seen as objective and somewhat cold. However, in reality color is tightly bound to math.

Most of us think of color as an inherent property of an object. There’s some truth to that idea. In the same light an object will always appear to be the same color no matter how many times we look at it. But at the same time there’s more to the story. Every object absorbs and reflects light in different ways.

Illustration of the suns white light being reflected by a red apple

It’s this reflected light which we’re recognizing as a color. It’s not so much that an apple is intrinsically red. Rather, an apple reflects red light. And this light is also a physical property which can be mathematically defined. But don’t be fooled by the term physical. Light exists as waves on a very small scale of size. This tiny size is known as a nanometer or nm. Visible light exists from 400 to 700 nanometers. Meanwhile the smallest human hair has a diameter of 80,000 nm.

We’re not aware of the fact that objects are continually bouncing tiny particles and waves of light into our eyes. Nor are we consciously aware of the cone cells in our eyes translating specific wavelengths of light into color. But when we take a moment to understand each color and frequency, we can broaden our understanding of the beautiful world which surrounds us.

Violet: 400 – 450 nm

Violet light has a wavelength between 400 and 450 nm. The human eye tends to easily mistake violet and purple. However, the colors are quite distinct. Purple is a mix of red and either blue or violet. The fact that both colors are so similar makes it difficult to firmly say whether or not any ancient group was using violet or purple. However, with that in mind we can say that some of humanity’s earliest associations with the color violet come from the bronze age.

The Phoenician city of Tyre made a special dye from local shellfish. This dye was beautiful, much desired and quite expensive. It’s thought that this is where an association between violet or purple and nobility first began. Only the most wealthy could afford to have clothing colored with this expensive dye from Tyre.

Blue: 450 – 500 nm

Blue light has a wavelength between 450 and 500 nm. You might be surprised to find out that a pure blue color isn’t quite as common in nature as it would appear. For example, the blue of the sky is due to rayleigh scattering rather than pure blue light. Do you, or someone you know, have blue eyes? If so, don’t assume it’s because of blue pigment.

People who seem to have blue eyes actually lack any pigment in the stroma of their eyes thanks to a genetic mutation. Light hitting someone’s clear stroma will scatter. Blue light in this mix will appear more prominent thanks to the tyndall effect. This all comes together to make it seem like someone with a clear stroma has blue eyes.

Cyan: 500 – 550 nm

We find cyan between 500 and 550 nm. Cyan might not be referenced by name as much as most of the colors on this list. However, cyan is still quite prevalent in the world. We also see it called by some other names including aquamarine or electric blue.

As you might expect, we do see aquamarine in aquatic environments. It’s especially common when we look out at shallow waters over a sandy beach. However, you’d have to hop over a few planets to see our solar system’s greatest concentration of cyan colored vistas. If someone could look out at the skies of Uranus he’d see a beautiful cyan sky. The colorful atmosphere of Uranus is thanks to its plentiful methane.

Green: 550 – 580 nm

We find green between 550 and 580 nm. The color is often associated with nature and it’s easy to see why. Go into a forest and you’ll find yourself presented with wide swaths of green leaves.

The greenery is due to the fact that plants are using their leaves to absorb energy from the sun. Plants primarily absorb red, and to a lesser extent blue light. The reflected light is why we see leaves as green.

Yellow: 580 – 600 nm

Yellow sits between 580 and 600 nm. Ask people to think of yellow things within their life and they’ll probably list the sun somewhere in their recitation. And to be sure, the sun certainly does appear to be yellow. But as we’ve seen time and again color is often due to reflection and refraction of light.

The sun actually burns a bright white, but the earth’s atmosphere scatters sunlight as it pours down on us. Yellow is among the least affected colors during this process. The result is an orb which appears yellow or orangish red at various times of the day.

Orange: 600 – 650 nm

Orange can be found between 600 and 650 nm. We associate the color orange with a wide variety of different things. However, the number one association for most people will be the fruit of the same name.

Oranges have their distinctive color due to the presence of compounds called carotenoids. And carotenoids tend to reflect light at a higher wavelength. This gives both oranges and carrots their distinctively bright coloring.

Red: 650 – 700 nm

Red has a wavelength between 650 and 700 nm. We find red represented in a vast number of different places in the world. However, we’ve already touched on one of the most important uses of red light. Red light plays a vital part in the growth of plants.

Most plants depend on a mix of red and blue light. The blue light promotes chlorophyll production. The red light is important for root growth, seed germination, flowering and seed production. Healthy leaves usually have a green appearance because they absorb red and blue light so well while reflecting green.

The Physics of Everyday Life

The examples we’ve looked at highlight how intertwined color and physics are. It’s easy to assume that math has to be dull. But in reality math and physics form the framework of all of life’s most beautiful colors. By understanding why various colors are so prevalent under certain conditions, we can come to see just how beautiful the universe really is.

Infographic of visible light spectrum with overview of color wavelengths