The Visible Light Spectrum

Understanding the Parts of White Light

This is the visible spectrum of light.
This is the visible spectrum of light. Maureen P Sullivan, Getty Images

The visible light spectrum is the section of the electromagnetic radiation spectrum that is visible to the human eye. It ranges in wavelength from approximately 400 nm (4 x 10-7 m, which is violet) to 700 nm (7 x 10-7 m, which is red). It is also known as the optical spectrum of light or the spectrum of white light.

The wavelength (which is related to frequency and energy) of the light determines the perceived color.

The ranges of these different colors are listed in the table below. Some sources vary these ranges pretty drastically, and the boundaries of them are somewhat approximate as they blend into each other. The edges of the visible light spectrum blend into the ultraviolet and infrared levels of radiation.

Most light that we interact with is in the form of white light, which contains many or all of these wavelength ranges within them. Shining white light through a prism causes the wavelengths to bend at slightly different angles due to optical refraction. The resulting light is, therefore, split across the visible color spectrum.

This is what causes a rainbow, with airborne water particles acting as the refractive medium. The order of wavelengths (as shown to the right) is in order of wavelength, which can be remembered by the mnemonic "Roy G. Biv" for Red, Orange, Yellow, Green, Blue, Indigo (the blue/violet border), and Violet.

If you look closely at a rainbow or spectrum, you may notice that cyan also appears fairly distinctly, between green & blue. It's worth noting most people cannot distinguish indigo from blue or violet, so many color charts omit it entirely.

Colors and Wavelength of Visible Light

This table gives the wavelength ranges for the colors of the spectrum:

The Visible Light Spectrum
ColorWavelength (nm)
Red625 - 740
Orange590 - 625
Yellow565 - 590
Green520 - 565
Cyan500 - 520
Blue435 - 500
Violet380 - 435

By using special sources, refractors, and filters, you can get a narrow band of about 10 nm in wavelength that is considered monochromatic light. Lasers are special because they are the most consistent source of narrowly monochromatic light that we can achieve. Colors consisting of a single wavelength are called spectral colors or pure colors.

Colors Beyond the Visible Spectrum

Some animals have a different visible range, often extending into the infrared range (wavelength greater than 700 nm) or ultraviolet (wavelength less than 380 nm). For example, bees can see ultraviolet light, which is used by flowers to attract pollinators. Birds can also see ultraviolet light and have markings visible under a black (ultraviolet) light. Among humans, there is variation between how far into red and violet the eye can see. Most animals that can see ultraviolet can't see infrared.

Also, the human eye and brain and distinguish many more colors than those of the spectrum. Purple and magenta are the brain's way of bridging the gap between red and violet. Unsaturated colors, like pink and aqua, are distinguishable.

Colors like brown and tan are also perceived by people.

Edited by Anne Marie Helmenstine, Ph.D.