Lesson 43: Transverse & Longitudinal Waves

When you hear the word “waves” you probably have visions of hanging ten off of Waikiki.

• Although these are “waves”, we will be looking at a more detailed definition of waves in the following sections.
• Specifically we will be looking at mechanical waves, waves that travel through a medium (substance) like air, water, a rope, etc.

Always remember that any wave we discuss is just is a way of transferring energy from one place to another.

• The difference between waves and regular matter moving around to transfer energy, is that a wave pulse starts in one spot and, except for a small amount of movement, the particles of the wave stay in one spot.
• In contrast, to transfer energy with a particle directly, that particle must actually move (kinetic energy) and strike something.

There are essentially two main types of waves (although there is a third called "surface waves" we don’t need to study them):

## Transverse Waves

Transverse waves are the waves that have the classical wave shape everyone thinks of when they imagine a wave.

• Particles of the medium move perpendicular to the direction the transverse wave itself is moving. For example, if the wave is moving to the right, the particles of the medium are moving up and down.
• Try shaking a skipping rope or other long rope to get a wave like the one pictured above. Tie a ribbon to one spot on the rope and watch just the ribbon… you will see it bounces only up or down, while the wave travels away from you. They are moving perpendicular to each other.
• The best examples of transverse waves are plucking the strings on any stringed instrument.

## Longitudinal Waves

Most people don’t usually picture longitudinal waves when they think of a wave.

• Imagine securing one end of a Slinky to a wall.
• Now stretch out the Slinky by holding onto one end and walking backwards.
• Stop walking. While holding onto the end still, bunch up some of the coils in your hand. Let go.
• "Sproing" is of course a highly scientific word!
• The Slinky will “sproing” back and forth away and towards you. There are areas where the Slinky is compressed, and parts where it is expanded. The “sproing” or longitudinal wave is moving parallel to the direction the particles are moving.
• In this wave, the particles are moving left and right parallel to the motion of the wave.

The best example of this kind of wave is sound.

• When you talk you are pushing, and sometimes not pushing, air out of your lungs past your vocal cords.
• There will be parts where the air particles are squished together (compressions), and others where they are allowed to separate (expansions).

you can see some transverse and longitudinal waves by clicking here. Requires Windows Media Player 9 or later and a broadband connection (dial-up connection not recommended).