Sound Needs a Medium for Propagation
When you call up your friend who is standing at a distance, your friend is able to hear your voice. How does the sound travel to her? Can you think of an explanation? Is it possible that the decreasing amount of air in the tumbler had something to do with decreasing loudness of the ring? Indeed, if you had been able to suck all the air in the tumbler, the sound would stop completely. Actually, sound needs a medium to travel. When air has been removed completely from a vessel, it is said that there is vacuum in the vessel. The sound cannot travel through vacuum.
Does sound travel in liquids? Let us find out.You can also perform the above activity by placing your ear at one end of a long wooden or metallic table and asking your friend to gently scratch the other end of the table.We find that sound can travel through wood or metal. In fact, sound can travel through any solid. You can perform interesting activities to show that sound can also travel through strings. Recall if you made a toy telephone. Can you say that the sound can travel through strings?We have learnt so far that vibrating objects produce sound and it is carried in all directions in a medium. How do we hear it?
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Sound - Notes
4. Sound Needs a Medium for Propagation
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7. Sound is Produced by a Vibrating Body
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