21. Intext questions II

 

When the school bell rings, the adjacent particles in air are forced to vibrateforced to moveforced to separate simultaneously. This disturbance leads to the formation of a sound wave and when the bell moves forward, it pushes the air in front of itpulls the air behind it. This forms a region of low pressureshigh pressures known as compression. When the bell moves backwards, a region of high pressurelow pressure known as rarefaction is created.

 

In this way the bell continues to move forward and backward which produces a series of compressions and rarefactions. This leads to the sound of a bell when it propagates through air.