The wavelength of a wave is the distance from one crest to the next. Click on image for full size (106K GIF) Windows to the Universe original artwork.

Have you ever seen waves in the ocean or on a lake? If you watch the waves, you will see that they come one after another after another. Each wave is about as far away from the one in front of it as it is from the one behind it.

We can measure how far it is between the waves. Usually we measure from the top of one wave to the top of the next. The distance we measure is called the wavelength of the wave. The waves we see at a beach usually have a wavelength of 10 meters (33 feet) or longer.

Did you know that sound moves through the air in waves? Sound waves that people can hear have wavelengths between about 2 cm (an inch) and 17 meters (56 feet).

Light is also a kind of wave. Waves of electricity and magnetic force move through space. Those waves are called electromagnetic waves. Light is one kind of electromagnetic wave. Light waves are very, very, very short. Light waves have wavelengths between 400 and 700 nanometers (a nanometer is one billionth of a meter!).