Color and Light

The human eye detects color using three types of cone cells sensitive to red, green, and blue light.

Rainbows form when sunlight bends and reflects inside countless tiny water droplets in the air.

A prism splits white light into a spectrum because each wavelength bends by a different amount.

Shadows appear when an opaque object blocks light from reaching a surface behind it.

Mirrors reflect light because a thin metal coating bounces most incoming rays straight back.

A red apple looks red because its skin absorbs most colors and reflects red wavelengths.

White objects look white because they reflect nearly all wavelengths of visible light equally.

Black surfaces look dark because they absorb most of the visible light that falls on them.

Sunlight contains all the colors of the visible spectrum blended together into white light.

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

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.

Mixing yellow and blue paint produces green, which surprises people taught that mixing light works differently.

Pigments create color by subtracting wavelengths, while lights create color by adding wavelengths together.

A shadow's edges grow blurrier as the light source becomes larger or moves farther away.

The darkest part of a shadow is called the umbra, while the softer edge is the penumbra.

A periscope uses two mirrors to let a viewer see over an obstacle.

A mirror swaps left and right in reflections, though it really reverses front and back.

Kaleidoscopes create symmetrical patterns by reflecting light between angled mirrors inside a tube.

Water bends light, which makes a straight straw in a glass look broken or shifted.

Mirages appear on hot roads when layers of air bend light from the sky toward the ground.

A rainbow is actually a full circle, but the ground usually hides the lower half.

Double rainbows happen when light reflects twice inside each droplet, reversing the color order.

You never see a rainbow from directly overhead because the geometry requires looking away from the sun.

Red light bends least through glass, while violet light bends the most.

The color orange takes its name from the fruit, which had the word first.

Purple and violet describe similar hues, though violet refers to a single wavelength of light.

Many languages have fewer basic color words than English, sometimes grouping blue and green together.

Turquoise sits between blue and green on the spectrum and is named after a gemstone.

Gold and silver describe metallic surface appearances rather than one particular wavelength of light.

The color of a flame changes with temperature, shifting from red toward blue as it gets hotter.

Optical illusions trick the brain by exploiting the shortcuts it uses to interpret light and edges.

Afterimages appear when staring at a bright color fatigues the cone cells responding to that hue.

A gray square looks lighter on a black background than the same square on a white one.

Neon colors seem to glow because they reflect more light than ordinary dyes can.

Fluorescent materials absorb invisible ultraviolet light and re-emit it as visible color.

Glow-in-the-dark objects store light energy and release it slowly over several minutes.

Polarized sunglasses reduce glare by blocking light waves vibrating in one particular direction.

Soap bubbles show shifting colors because thin films interfere with reflected light waves.

Oil on wet pavement shows a rainbow pattern for the same reason thin soap films do.

A peacock feather gets iridescent color from microscopic structures rather than from pigment.

Butterfly wings often shimmer with structural color produced by tiny scales instead of dyes.

Blue pigments are rare in nature, so most blue animals rely on structure instead.

Cameras capture color by filtering light through red, green, and blue sensors.

Printed images use cyan, magenta, yellow, and black ink to reproduce many colors.

Stop signals are usually red because the color stands out against most natural backgrounds.