Types of Waves

Types of Waves

By Thomas Rottet

The wave is a popular actiity at sporting events!

​

The wave mimics the up-and-down
pattern of movement created by a light wave.
However, other types of waves move differently.

In this lesson, you will learn about how
two distinct types of waves move.

​

Waves carry energy from one place to another. However, there are two different ways that waves can move. Depending on the movement pattern, waves can be classified as:

• transverse

• longitudinal

​

A transverse wave is a wave that vibrates perpendicular to the direction its energy moves.

• The wave vibrates up and down.

• The energy the wave carries travels sideways, at a right angle to the vibration.

As the energy moves sideways while the wave vibrates up and down, it creates the curved path that scientists use to model EM waves.

​

Transverse waves have curving crests and troughs. One way to understand this movement is to think about a roller coaster. The wave pattern is like the track. The car of a roller coaster is like the traveling wave. Overall, the car is moving toward the left side of the screen, like the wave's energy, but it also moves up and down through crests and troughs as it travels.

Remember that models help you understand a concept. A roller coaster is not exactly the same as a transverse wave, but the model helps you to understand how waves behave.

Multiple Choice

What part of this model represents the direction in which the wave vibrates?

• 1

• 2

• 3

• 4

​Note that the source of the transverse wave in the hotspot above is a television that produces visible light. Visible light is one type of light wave. Light includes all of the types of waves on the EM spectrum. All types of light are transverse waves.

​

Light waves can travel through some types of matter, such as air, water, and glass. Light can also travel through the vacuum of space. Visible light and UV rays from the Sun travel through space as radiation to reach Earth.

Solid objects often block light waves. For example, the Lehigh Tunnel on the PA Turnpike allows cars to drive through Blue Mountain. If you are streaming music while you enter the tunnel, you will drive part of the tunnel in silence. The mountain above the tunnel blocks the waves that carry the music data to your phone.

Multiple Select

Which of the following can light waves travel through? There are 3 correct choices.

• The vacuum of space

• Glass

• Air

• A mountain

​All light waves—visible and invisible—are transverse waves. Light waves can travel through space, air, and some liquids. Many solid objects block light waves. Continue on to learn about longitudinal waves.

​

Longitudinal Waves

A longitudinal wave is a wave that vibrates in the same direction that its energy moves. Longitudinal waves are often called compression waves because of the way molecules compress as the waves travel through them.

Longitudinal waves require a medium to travel through. A medium contains matter. Common mediums that longitudinal waves travel through include air, water, and solid objects.

​

Unlike transverse waves, longitudinal waves do not produce crests and troughs. Instead, longitudinal waves produce areas of compression and expansion.

• Compression occurs when the vibration causes molecules in the medium to press together, or compress.

• Expansion, sometimes called rarefaction, occurs when the vibration spreads molecules in the medium apart.

Expansion and compression occur because the direction the wave vibrates is parallel to the direction the energy moves.

​

Both longitudinal and transverse waves have wavelengths.

• Recall that the wavelength of a transverse wave runs from crest to crest or from trough to trough.

• A wavelength in a longitudinal wave runs from compression to compression or from expansion to expansion.

​Catching a Sound Wave

​The video below discusses sound waves. As you view the video, think about how sound waves move.

Multiple Choice

When you shout out the window while driving through a tunnel, what medium does the sound of your shout pass through?

• Air

• Concrete

• Water

• Vacuum

​

Sound waves can travel through a variety of mediums.

• Your ears detect sound waves that travel through the air.

• Whales communicate using sound waves that travel up to 16,000 km through water.

• Elephants use their feet to send signals up to 32 km through the ground.

Compression waves carry energy through a medium.

​The video below reviews the differences between transverse and longitudinal waves. As you view the video, pay attention to the way the waves transfer energy. Think about how you can tell the difference between the two types of waves.

​Video: The differences between longitudinal and transverse waves

Multiple Choice

True or false:

The wave, as it is performed at sporting events, is a compression wave.

• True

• False

​Transverse and longitudinal waves differ in several ways. However, the waves also have some things in common. Both transverse and longitudinal waves carry energy. Transverse and longitudinal waves also both have amplitude. The greater the amplitude, the more energy the wave carries.