Jessica Crabtree

Making Waves

It turns out the secret of color is all in the waves – light waves, that is. Light, like matter, is made up of tiny particles – but unlike matter these are not atoms or molecules but tiny packets of energy called photons. Oddly, light has a dual nature that makes it behave both like matter (because it is made of particles) and like wave energy, such as vibration or sound. All of the properties of light most familiar to us – including color – come from this wave aspect. All of the colors we see are produced by the varying height and depth of light wavelengths and the speed at which they happen to be traveling.

Human beings have a limited range of perception, so we can only see a narrow range of light energy to interpret as “color.” This range is known as visible light. These colors are arranged in a band known as a spectrum, with each color – just like an FM radio station – sorted by its wavelength and frequency.

Newton and the Prism

For instance, red at one end of the spectrum has a very low frequency and a very high wavelength. Any light with a lower frequency is impossible for the human eye to detect – hence “infrared” or “below red” on the light spectrum. Since all colors are exactly measurable, we know that light with a frequency ranging from 480 to 405 THz (that’s Teraherz, a unit for measuring radiation of energy) will appear red to us. The same is true for wavelength; if light has wavelengths ranging in size from 630 to 740 nanometers – or about 33,000 waves to an inch – our brains will interpret it is red.

Violet, on the other hand, has a very low wavelength and a very high frequency; anything higher is known as “ultra-violet” light. This high frequency means that ultra-violet light can carry a lot more energy – enough in some cases to be dangerous to our health, like some of the energy that radiates from our sun.

(click to enlarge)

The colors in the spectrum band fade into one another, because they are all part of the spectrum of visible white light. (Remember, white is not a color – not because it is “blank” but because it contains all the colors. Isaac Newton discovered this by dividing light into its principal colors using a prism, as seen above.) For convenience, we divide the color band into separate color ranges or color groups, in order of frequency and wavelength, as we would see them in a rainbow or prism: red, orange, yellow, green, blue, indigo, and violet (or as you might have read in your first science textbook, “ROY G. BIV – the rainbow man”!)

Artists have found that the most practical way of representing the visible spectrum is in a continuous circle, which we know as a color wheel.

Color wheel showing primary, secondary, and tertiary colors