Longitudinal Waves

14

14.1 Introduction ESBGD

In Grade 10 we studiedpulses and waves. We looked at transverse waves more closely. In this

chapter we look at another type of wave called longitudinal waves. In transverse waves, the motion of

the particles in the medium were perpendicularto the direction of the wave. In longitudinal waves,

the particles in the medium move parallel (in the same direction as) to the motion of the wave.

Examples of transverse waves are water waves orlight waves. An exampleof a longitudinal wave isa

sound wave.

See introductory video:VPkqn at http://www.everythingscience.co.za

14.2 What is a longitudinal wave? ESBGE

DEFINITION: Longitudinal waves

A longitudinal wave is awave where the particles in the medium move parallel to the

direction of propagationof the wave.

When we studied transverse waves we looked at two different motions:the motion of the particles of

the medium and the motion of the wave itself. We will do the same for longitudinal waves.

The question is how dowe construct such a wave?

To create a transverse wave, we flick the end offor example a rope up and down. The particlesmove

up and down and returnto their equilibrium position. The wave moves from left to right and will be

displaced.

flick rope up and downat one end

A longitudinal wave is seen best in a spring thatis hung from a ceiling. Do the following investigation

to find out more about longitudinal waves.

Activity: Investigating longitudinal waves