Puricare Industrial Enterprises: THE VISIBLE SPECTRUM - Wavelengths and Colors - Light from 400–700 nanometers (nm) is called visible light, or the visible spectrum. Light outside this range may be visible to other organisms but cannot be perceived by the human eye. Colors of light that correspond to narrow wavelength bands (monochromatic light) are the pure spectral colors learned using the ROYGBIV acronym: red, orange, yellow, green, blue, indigo, and violet. Some people can see further into the ultraviolet and infrared ranges than others, so the "visible light" edges of red and violet are not well-defined. Violet light has the shortest wavelength, which means it has the highest frequency and energy. Red has the longest wavelength, the shortest frequency, and the lowest energy. The spectrum was first described with seven colors. The visible spectrum does not encompass all the colors humans perceive because the brain also perceives unsaturated colors and colors that are a mixture of wavelengths. Mixing colors on a palette produces tints and hues not seen as spectral colors.

Graded watercolor wash background in pink tones

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The Visible Spectrum

Wavelengths and Colors

by Anne Marie Helmenstine, Ph.D.

The human eye sees color over wavelengths ranging roughly from 400 nanometers (violet) to 700 nanometers (red).

Light from 400–700 nanometers (nm) is called visible light, or the visible spectrum, because humans can see it.

Light outside this range may be visible to other organisms but cannot be perceived by the human eye.

Colors of light that correspond to narrow wavelength bands (monochromatic light) are the pure spectral colors learned using the ROYGBIV acronym: red, orange, yellow, green, blue, indigo, and violet.

Wavelengths of Visible Light

Some people can see further into the ultraviolet and infrared ranges than others, so the "visible light" edges of red and violet are not well-defined.

Also, seeing well into one end of the spectrum doesn't necessarily mean you can see well into the other end of the spectrum.

You can test yourself using a prism and a sheet of paper.

Shine a bright white light through the prism to produce a rainbow on the paper. Mark the edges and compare the size of your rainbow with that of others.

The wavelengths of visible light are:

Violet: 380–450 nm (688–789 THz frequency)

Blue: 450–495 nm

Green: 495–570 nm

Yellow: 570–590 nm

Orange: 590–620 nm

Red: 620–750 nm (400–484 THz frequency)

Violet light has the shortest wavelength, which means it has the highest frequency and energy.

Red has the longest wavelength, the shortest frequency, and the lowest energy.

The Special Case of Indigo

There is no wavelength assigned to indigo. If you want a number, it's around 445 nanometers, but it doesn't appear on most spectra.

There's a reason for this. English mathematician Isaac Newton (1643–1727) coined the word spectrum (Latin for "appearance") in his 1671 book "Opticks."

He divided the spectrum into seven sections — red, orange, yellow, green, blue, indigo, and violet — in keeping with the Greek sophists, to connect the colors to days of the week, musical notes, and the known objects of the solar system.

So, the spectrum was first described with seven colors, but most people, even if they see color well, can't actually distinguish indigo from blue or violet.

The modern spectrum typically omits indigo. In fact, there is evidence Newton's division of the spectrum doesn't even correspond to the colors we define by wavelengths.

For example, Newton's indigo is the modern blue, while his blue corresponds to the color we refer to as cyan. Is your blue the same as my blue? Probably, but it may not be the same as Newton's.

Colors People See That Aren't on the Spectrum

The visible spectrum does not encompass all the colors humans perceive because the brain also perceives unsaturated colors (e.g., pink is an unsaturated form of red) and colors that are a mixture of wavelengths (e.g., magenta).

Mixing colors on a palette produces tints and hues not seen as spectral colors.

Colors Only Animals Can See

Just because humans can't see beyond the visible spectrum doesn't mean animals are similarly restricted.

Bees and other insects can see ultraviolet light, which is commonly reflected by flowers. Birds can see into the ultraviolet range (300–400 nm) and have plumage visible in UV.

Humans see further into the red range than most animals. Bees can see color up to about 590 nm, which is just before orange starts. Birds can see red, but not as far toward the infrared range as humans.

Some people believe the goldfish is the only animal that can see both infrared and ultraviolet light, but this notion is incorrect. Goldfish cannot see infrared light.

Anne Marie Helmenstine, Ph.D.

Introduction

Ph.D. in biomedical sciences from the University of Tennessee at Knoxville - Oak Ridge National Laboratory.

Science educator with experience teaching chemistry, biology, astronomy, and physics at the high school, college, and graduate levels.

ThoughtCo and About Education chemistry expert since 2001.

Widely-published graphic artist, responsible for printable periodic tables and other illustrations used in science.

Experience

Anne Helmenstine, Ph.D. has covered chemistry for ThoughtCo and About Education since 2001, and other sciences since 2013. She taught chemistry, biology, astronomy, and physics at the high school, college, and graduate levels. She has worked as a research scientist and also abstracting and indexing diverse scientific literature for the Department of Energy.

In addition to her work as a science writer, Dr. Helmenstine currently serves as a scientific consultant, specializing in problems requiring an interdisciplinary approach. Previously, she worked as a research scientist and college professor.

Education

Dr. Helmenstine holds a Ph.D. in biomedical sciences from the University of Tennessee at Knoxville and a B.A. in physics and mathematics with a minor in chemistry from Hastings College. In her doctoral work, Dr. Helmenstine developed ultra-sensitive chemical detection and medical diagnostic tests.

ThoughtCo and Dotdash

ThoughtCo is a premier reference site focusing on expert-created education content. We are one of the top-10 information sites in the world as rated by comScore, a leading Internet measurement company. Every month, more than 13 million readers seek answers to their questions on ThoughtCo.

For more than 20 years, Dotdash brands have been helping people find answers, solve problems, and get inspired. We are one of the top-20 largest content publishers on the Internet according to comScore, and reach more than 30% of the U.S. population monthly. Our brands collectively have won more than 20 industry awards in the last year alone, and recently Dotdash was named Publisher of the Year by Digiday, a leading industry publication.

https://www.thoughtco.com/understand-the-visible-spectrum-608329

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