# Lakhmir Singh Solutions Class 9 Physics Solutions for Exercise in Chapter 5 - Sound

Question 64 Exercise

a) Explain the terms ‘compression’ and ‘rarefactions’ of a wave. What type of waves consists of compression and rarefaction?

b) A worker lives at a distance of 1.32 km from the factory. If the speed of sound in the air be 330 m/s how much time will the sound of factory siren take to reach the worker?

a) Compression is a part of a longitudinal wave in which the particles of the medium are close to each other which reduces the volume of the medium.

Rarefaction is also a part of a longitudinal wave in which the particles of the medium are farther apart from each other which increases the volume of the medium.

b) Speed = 330 m/s

Distance = 1.32 km = 1320 m

Time = distance/speed = 1320/330 = 4s

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