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Explain why ( or how ) : (a) in a sound wave, a displacement node is a pressure antinode and vice versa, (b) bats can ascertain distances, directions,nature and sizes of the obstacles without any "eyes". (c ) a violine note and sitar note may have the samefrequency,yet we can distinguish between the two notes. (d) Soils can support both longitudinal and transverse waves, but only longitudinal waves can propagate in gases and (e ) The shape ofa pulse gets distorted during during propagation in a dispersivemedium. |
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Answer» Solution :(a) Node (N ) is a pointwherethe amplitude of oscillation is 0. ( and pressure is maximum ) Antinode ( A) is a point where the amplitude of osciallation is maximum ( and pressureis MIN). These nodes & antinodes do not coincide with pressure nodes & antinodes. Infact , N coincides with pressure antinode and A coincides with pressure node,as is clear from the definitions. (b)Bats EMIT ultrasonic wave of large frequencies, when these waves are reflected from the obstacles in their path, they give them the idea about the distance, direction , size & nature of the osbtacle. (c )Thoughthe violin note and sitar note have the same frequency, yet the over tones produced and their reactivestrengths are different in the two notes that is WHYWE can distinguish BETWEENTHE two notes. (d)This is because solids have both, the elasticity of volume and elasticity of SHAPE where asgases haveonly the volume elasticity. (e ) A sound pulseis a combination of waves of different wavelenths. As waves of different wavelengths travelsin a dispersemedium with different velocities,therefore the shape of the pulsegets distorted. |
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