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Homework Help: Sound wave of wavelength

  1. May 30, 2005 #1
    A sound wave of wavelength 0.70 m and velocity 330 m/sec is produced for .50 s.

    A) What is the frequency of the wave?
    B) how many complete waves are emitted in this time interval?
    c) after .50 s, how far is the front of the wave from the source of the sound?

    AnsA) V= (Lambda)(f)
    f= V/Lambda = 330/.70= 471.4 Hz

    Ans b) I dont know how to do this.. is this the frequency?

    Ans c) Lambda = (.50) ( 330) = 165 m

    Are the above answers correct? also, i'd appreciate it if you guys could help me for the second question ( part b )

  2. jcsd
  3. May 30, 2005 #2
    Seems correct, for question B think of it like this. If you emit the wave for a time so that it passes 1.4m how many complete waves will you have emitted?
    Then if you emit for a time so that it passes 1.5m? And if it passes lambda*v?
  4. May 30, 2005 #3
    (330) ( .50) = 165 m ...

    165/ .70 = 235 waves?

    damn. that doesnt sound right..
  5. May 30, 2005 #4

    Doc Al

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    Staff: Mentor

    Think of it this way. The frequency (which you found in part a) is the number of cycles (or waves) produced each second. So... the number of waves produced in a given time must equal [itex]f \times t[/itex].
  6. May 30, 2005 #5
    471.4 waves produced each second.

    therefore, in half second = 471.4 * .5 ( f x t) = 235 waves?

    i still get the same answer... doh..
  7. May 30, 2005 #6

    Doc Al

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    Staff: Mentor

    You'd better get the same answer!
  8. May 30, 2005 #7
    oh ok .. lol.. i thought the answer was wrong.. alright thanks a lot...finally understood it :)
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