Selina Concise ICSE Solutions for Class 8 Physics Chapter 7 Sound • SOUND: “Is energy which produces in us the sensation of hearing.” It is produced by vibration of body. • Sound needs a medium for its propagation. Sound cannot travel in vacuum. • Speed of sound is maximum in solids. 5000 ms-1 in steel, in water 1500 ms-1 and in air it is least 330 ms-1 nearly. • When a body vibrates, the particles of medium also start vibrating and K.E. of particles changes into potential energy and P.E. into K.E. This is why sound in energy. • Sound travels in a medium in the form of wave. • Longitudinal wave : When the particles of medium move in the direction of motion of wave by forming compression and rarefaction. • AMPLITUDE : “The maximum displacement of the particle of medium on either side of mean position.” • TIME PERIOD: “The time taken by a particle of...
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