Q20 of 20 Page 73

Draw a curve showing density or pressure variations with respect to distance for a disturbance produced by sound. Mark the position of compression and rarefaction on this curve. Also define wavelengths and time-period using this curve.


Wavelength is the distance between two consecutive compressions or two consecutive rarefaction of a wave sound. Wave length is represented by Greek letter λ (lambda). The SI unit of wavelength is metre (m).


Time period is the time taken to travel the distance between any two consecutive compression or rarefaction from a fixed point. The time period of sound wave is represented by letter ‘T’. The SI unit of time period is second (s).


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Represent graphically by two separate diagrams in each case

(i) Two sound waves having the same amplitude but different frequencies?


(ii) Two sound waves having the same frequency but different amplitudes.


(iii) Two sound waves having different amplitudes and also different wavelengths.

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Establish the relationship between speed of sound, its wavelength and frequency. If velocity of sound in air is 340 m s-1, calculate

(i) Wavelength when frequency is 256 Hz.


(ii) Frequency when wavelength is 0.85 m.