improvement in food resource class 9- new















 

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sound, class 9

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  Sound: it is a kind of energy which gives us sensation of hearing. The sound is produced by vibrating objects. They travel from one place to another in the form of waves. Hence, the name sound waves. Sound waves are longitudinal mechanical wave.   Wave and particle motion of waves Mechanical waves are waves that travel through a material medium. It is of two types: depending on the direction of motion of the particle of the medium and the wave propagation: Transverse waves Particle motion is to perpendicular the direction of wave motion. This type of wave is a mechanical wave called a transverse wave. E.g.: Light, or even  Mexican wave in a stadium. Longitudinal waves When the particles of the medium travel parallel to the direction of the wave motion by means of successive compression or rarefaction. It is also a mechanical wave. Example: a ...
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