GO IN DEPTH

# Longitudinal and Transverse Waves Teacher Sheet

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### Introduction

In this part of the lesson, students learn more about sound waves by studying some online resources. This sheet provides answers to the questions about the wave models video.

Introduction to Wave Models
What is a sound wave?
A sound wave is created when a source of energy, such as a clap, a drum roll, or the bow of a violin against strings, causes vibrations in the medium in which it is traveling. The medium can be a solid, a liquid, or the air.

The video showed one model of how sound travels. Can you describe that model?
The video presented a model of a row of balls in which one was struck lightly with a mallet. This started a chain reaction, where each ball hits the one next to it. This series of vibrating balls is a concrete model of how sound waves travel.

What is a longitudinal wave? Draw a picture of this wave and describe it in words.
A longitudinal wave is characterized by a series of compressed sound molecules, followed by rarefied air, in which the molecules are farther apart. This wave can be drawn as follows:

What is a transverse wave? Draw a picture of this wave and describe it in words.
A transverse wave moves across air or water at a right angle to the direction in which the waves are traveling. Some parts of the wave are high, while others are low. The highest parts of the wave are called crests, and the lowest parts are called troughs. This wave can be drawn as follows:

In the 19th century, scientists depicted sound waves as transverse waves. How were they able to do that? What parts of the waves are related?
The compressed air in longitudinal waves corresponds to the crest, while the rarefied air corresponds to the trough. By matching up those characteristics, it is possible to render longitudinal waves (sound waves) as transverse waves.

This teacher sheet is a part of the Properties of Sound Waves lesson.