Violet light has the shortest wavelength visible to humans, while red has the longest.

The longer version

Visible light runs from roughly 400 to 700 nanometres, with violet at the short end and red at the long end. Shorter waves pack more energy per photon, which is enough to drive certain chemical reactions, including the ones that fade dyes and sunburn skin.

Below violet lies ultraviolet, invisible to us but visible to bees and many birds; above red lies infrared, felt as heat. The boundary is not sharp and varies slightly between individuals. Human sensitivity also peaks in the middle, so a green light of modest power looks brighter than an equally powerful deep red one.

Where this entry sits

These facts explore how light behaves and how human eyes turn it into the colors we see. Along the way you meet rainbows, prisms, mirrors, shadows, lasers, and optical tricks that fool our vision every day. The full list sits on the Color and Light page, where every entry is listed in order.

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More From Color and Light

Eight more entries

The sky looks blue because air molecules scatter short blue wavelengths more than long red ones.

Sunsets often look red because sunlight travels through more air, which scatters away the blue light.

Laser light differs from ordinary light because its waves are aligned and share a single wavelength.

The traditional spectrum is often listed as seven colors, including red, orange, yellow, green, blue, indigo, and violet.

Most people cannot distinguish indigo from blue or violet in an ordinary rainbow.

Color blindness most often involves difficulty telling red from green rather than seeing no color at all.

Some animals, including many birds, see ultraviolet light that human eyes cannot detect.

Mixing red, green, and blue light in equal amounts produces white light on a screen.

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