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Waves and time?

  1. Nov 7, 2015 #1


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    Hi I want to create a thought experiment involving waves of any kind. I am going to create a thought experiment I am on a boat that is at rest in the ocean. I am standing on the boat measuring the size of the waves and the frequency. So I measure the wave along the side of my boat to have a length of 6 meters and a frequency of 1 per second. So i deduce the wave is traveling at 6 m/p/s (6 meters per second).

    Now I sail my boat at 6 m/p/s into the waves what is the outcome ?

    My Hypothesis is I would see the waves passing me by at twice the speed so the wavelength is 3 m/p/ half s (3 meters per half second) and as the wavelength half's the frequency doubles to 2 per second.
    So I conclude when you measure a wave you cannot add your speed to the wave as your motion has to be added or deducted from the wavelength which will effect the frequency and that is why the speed of light is constant to all observers. Any speed added by your motion is simply deducted from the wavelength and added to frequency. So the speed of light remains the same regardless of your motion. And it is not time that changes?
  2. jcsd
  3. Nov 7, 2015 #2


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    Why would the wavelenght be different ? Would the wavelength double if you go in the opposite direction ?
  4. Nov 7, 2015 #3
    First, what you are describing is called the classical (non-relativistic) Doppler effect. If you read about it, in any standard physics textbook, you will see where you are missing the point.
    Second, you made a big leap when you concluded that the speed of light is the same for all observers, by the strength of your argument, which is based on material (water) waves. The speed of water waves is not the same for all observers. You should know that there is no explanation for the speed of light being the same for all (inertial) observers. It is an axiom, the truth of which is borne out by the success of experiments.
  5. Nov 8, 2015 #4


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    so as the other two have suggested, the wavelength isn't changing, and for you nor is time
    so that leaves one choice for what is changing ... can you think what that is and why ?
    You have answered it without realising :wink:

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