Chapter 11

NCERT
Class 9
Science
Solutions
2. Describe with the help of a diagram, how compressions and rarefactions are produced in air near a source of sound.

Question:

Describe with the help of a diagram, how compressions and rarefactions are produced in air near a source of sound.

Answer:

Sound travels mostly through air. When a vibrating object moves forward, it compresses the air in front of it by applying force, which creates a region of high pressure that the region is called compression (C).[in figure] when this vibrating region starts moving away from the object, then the vibrating object moves forming a region of low pressure. This region is called rarefaction (R). As the object vibrates that is, moves back and forth with high intensity a series of compressions and rarefactions are generated in the air. Thus propagation of sound takes place in the air.

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