Source: Surf, Eric Wüstenhagen, Wikimedia Commons

Recall the following two important characteristics of waves:

1. Waves carry energy from one place to another without any transfer of mass.
2. All mechanical waves require a medium through which to travel. The medium is displaced and vibrates back and forth (or up and down) while the wave is moving, but once the wave is gone, the medium returns to its original position.

There are several different types of waves.

• Transverse waves- waves that move up and down
• Longitudinal waves- waves that move from side to side
• Surface waves – combination of transverse and longitudinal waves, found in water waves (like the one seen above)

Scientists classify waves as transverse or longitudinal by comparing the motion of the medium to the motion of the energy.

In the next few sections, you will learn about and compare these two types of waves.