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Homework Help: Wavelengths and Intesity

  1. Nov 8, 2008 #1
    1. The problem statement, all variables and given/known data

    Particles approximately 3.0 X 10-2 cm in diameter are to be scrubbed loose from machine parts in an aqueous ultrasonic cleaning bath. Above what frequency should the bath be operated to produce wavelengths of this size and smaller?

    2. Relevant equations

    speed of sound in water = 1500 m/s
    frequency = (speed of sound)/wavelength

    3. The attempt at a solution

    1500x10^4/3 = 5x10^6 Hz
    does this sound right?
  2. jcsd
  3. Nov 8, 2008 #2

    Yes, your calculations seem correct. But let me give you a tip, always do your calculations in SI units. You have the velocity in SI unit, why not change the diameter to SI instead of the other way around?

    In this case you are alright since frequency is dimensionless. However, in a case where the result is not dimensionless you will save time and minimized conversion errors risks having used SI units to begin with.

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