All around us we observe things that wiggle. Even atoms and particles too small to see wiggle. This wiggle motion is called a vibration. A vibration needs time to move back and forth. For example, when an orchestra plays a final note, it takes some time for the sound to fade away.

A wave is a wiggle that travels through space, and it takes time to move back and forth. Light and sound waves are forms of energy that move through space as a wave. These vibrations, or waves, carry energy. Waves can carry energy through solids, liquids, and gasses. For example, earthquake waves carry energy through the earth. Two buddies can move energy through a rope or spring, or energy can be transferred from a pebble thrown into a lake, making ripples in the water surface. Sound waves move the molecules that make up air, transmitting sound energy.

If you sit on a beach and watch the waves roll in, you can see them pound against the rocks and making ripples in the sand. They carry a lot of energy, transporting it from far out in the ocean. Yet a boat sitting 120 yards from shore merely bobs up and down. It is not carried in with the waves. Although waves keep coming in toward the shore, the water only moves up and down, or back and forth. Why?


The boat bobbing up and down is oscillating, moving back and forth or up and down in a repeated cycle. Many things oscillate: a swinging pendulum, the string on a violin, the air column of a flute, or a metronome to keep time while playing the piano.

Physicists call this disturbance of the ocean surface a periodic wave. It repeats the same pattern over and over. The world is full of periodic waves, but most of them are invisible. Sound waves, light waves, and electromagnetic waves surround us all the time, but we cannot see them with the naked eye.

Here is a general diagram of a wave. All waves, whether they are sound, light, earthquake, or water waves, have some things in common. Before we look at the unique characteristics of these waves, letís look at the things they all have in common and learn a few terms. And, of course, we must learn to measure wave characteristics in order to determine a few things about waves and how they work.