Transverse Waves

[Figure 1]

Can you guess what this picture shows? Here’s a hint: the objects in the picture have been magnified, and one of them is moving rapidly. The objects are guitar strings, and the moving string is the one on the bottom right. The string is moving because it has just been plucked. Plucking the string gave it energy, which is moving through the string in a mechanical wave. A mechanical wave is a wave that travels through matter. The matter a mechanical wave travels through is called the medium. The type of mechanical wave passing through the vibrating guitar string is a transverse wave.

What Is a Transverse Wave?

A transverse wave is a wave in which particles of the medium vibrate at right angles, or perpendicular, to the direction that the wave travels. Another example of a transverse wave is the wave that passes through a rope with you shake one end of the rope up and down, as in the Figure below. The direction of the wave is down the length of the rope away from the hand. The rope itself moves up and down as the wave passes through it.  

 

 

![Diagram of a longitudinal wave](https://dr282zn36sxxg.cloudfront.net/datastreams/f-d%3Adfd64cf3a1de72e4047180e67ed57638746b7c2d64bd6f01bb7faec9%2BIMAGE_THUMB_POSTCARD_TINY%2BIMAGE_THUMB_POSTCARD_TINY.1 "Diagram of a longitudinal wave" =500x203)

[Figure 2]

Q: When a guitar string is plucked, in what direction does the wave travel? In what directions does the string vibrate?

A: The wave travels down the string to the end. The string vibrates up and down at right angles to the direction of the wave.

Crests and Troughs

A transverse wave is characterized by the high and low points reached by particles of the medium as the wave passes through. The high points are called crests, and the low points are called troughs. You can see both in the Figure below.

![Crests and troughs of a transverse wave](https://dr282zn36sxxg.cloudfront.net/datastreams/f-d%3A578901a383f36549586e9148342cd73be28748394b680475d97f7b5a%2BIMAGE_THUMB_POSTCARD_TINY%2BIMAGE_THUMB_POSTCARD_TINY.1 "Crests and troughs of a transverse wave" =440x357)

[Figure 3]

S Waves

Transverse waves called S waves occur during earthquakes. The disturbance that causes an earthquake sends transverse waves through underground rocks in all directions away from the disturbance. S waves may travel for hundreds of miles. An S wave is modeled in the Figure below.

![Secondary waves are transverse waves](https://dr282zn36sxxg.cloudfront.net/datastreams/f-d%3Adc1dc3c9c1a390c3a207666afa7f2878622f23ad19d89d5c9bab7267%2BIMAGE_THUMB_POSTCARD_TINY%2BIMAGE_THUMB_POSTCARD_TINY.1 "Secondary waves are transverse waves" =500x277)

[Figure 4]

Summary

  • A transverse wave is a wave in which particles of the medium vibrate perpendicular to the direction that the wave travels.
  • The high points of a transverse wave are called crests, and the low points are called troughs.
  • S waves are transverse waves that travel through underground rocks during earthquakes.

Review

  1. What is a transverse wave?
  2. Sketch a transverse wave and label the crests and troughs.
  3. Infer how S waves might affect structures such as buildings.