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Longitudinal/Transverse oscillations

  1. Jun 12, 2012 #1


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    I was doing some questions on waves and I noticed that some particular questions didn't state whether a transverse or longitudinal disturbance was been driven through the medium. Such questions started like 'A sinusoidal wave moves along a string...' Do the equations that apply to transverse oscillations also apply to longitudinal waves or is there a difference somewhere?

    Also, I take it that the superposition principle also works for longitudinal waves, but this time the resultant amplitude will be parallel to direction of travel. I can't seem to envisage what a resultant amplitude would look like. It is easy for transverse since it stretches up / down by some factor - does this mean for longitudinal, it stretches left/ right ?

  2. jcsd
  3. Jun 12, 2012 #2

    Simon Bridge

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    Longitudinal oscillations in a spring are back and forth on the spring, yep. You see them as compression and rarefaction of the coils. In air - the sound waves are pressure waves. In water - you get transverse waves on the surface but the actual water molecules have a circular motion.

    With classical light the amplitude is the strength of the electric field ... is that transverse or longitudinal? Actual photons are just lumps of energy.

    Anything which can be described by wave equations obeys the rules for wave equations - so all waves obey the superposition principle. The wave equation is the same for each kind - it is the interpretation of the results that differs.

    So, basically, you seem to be thinking along the right lines.
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