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Finding amplitude from a diagram

  1. May 31, 2013 #1
    Hi all,

    This is not homework or coursework. I am not sure whether this question would be classed as homework or coursework because it is neither.

    I am using the AQA Physics A AS text book and attempting exercise 12.2 on page 177. In I am stuck on question 4 and I have absolutely no idea on how to find the amplitude. I have spent almost a day but still I haven't been able to find a matching answer. I was hoping someone here might help me.

    Here is the full question:

    For the waves in Figure 4,

    a) determine i the amplitude and wavelength, ii the phase difference between P and R, iii the phase difference between P and S.

    I can find the phase differences but not the wavelength and amplitude. I am probably missing something or have missed something and I am looking for a hint.

    I managed to find a preview of the page here

    I managed to get a screenshot of the page:

    Thank you.
  2. jcsd
  3. May 31, 2013 #2


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    Science Advisor

    The amplitude is the distance from the center line to a highest point on the graph. You can't tell from the graph because there is no vertical axis.
  4. May 31, 2013 #3

    I think you can by using the table, the phase difference formula and trigonometry. I have tried that but I don't get the right answer.
  5. May 31, 2013 #4
    If you understand the definition, the concept, I would not waste further time on this silly representation.


    good lord....They have managed to take a few simple questions and turn them to a convoluted

    What phase difference did you find??

    I have no idea how to scale the plots..either vertically or horizontally.

    'Distance from 0' as provided in the chart is actually incorrect....what they mean is the 'x' [horizontal distance] from o....

    I hope the concepts in the rest of the text are presented more clearly than here!!
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