InterviewSolution
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InterviewSolution
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Two sound sources S_1 and S_2 emit pure sinusoidal waves in phase. If the speed of sound is 350 m/s, (a) For what frequencies does constructive interference occur at P? (b) For what frequencies does destructive interference occur at P? |
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Answer» Solution :Path difference `Delta x = S_1P - S_2P` `=sqrt((2)^2 +(4)^2) - sqrt((1)^2 + (4)^2)` `=4.47 - 4.12 = 0.35m` (a) Constructive interference occurs when the path difference is an integer NUMBER of wavelength. `or Deltax = nlambda = (XV)/(f) or f = (n (v))/(Deltax)` where n = 1,2,3 ...... `:. f = (350)/(0.35), (2 xx 350)/(0.35), (3 xx 350)/(0.35),`....... `f = 1000Hz, 2000 Hz, 3000 Hz,...,` ETC. (b) Destructive interference occurs when the path difference is a half-integer number of wavelengths `Deltax = (2 n +1) lambda/2 n =0, 1,2,...(or ) Deltax = (2n +1) v/(2F)` `:.f = ((2n +1)v)/(2Deltax) =350/(2 xx 0.35) , (3 xx 350)/(2xx 0.35) , (5xx350)/(2 xx 0.35)`...... = 500 Hz, 1500 Hz, 2500 Hz |
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