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    Got stuck on a question, please see the link for the diagram *link removed*
    q5a
    Two loudspeakers are one metre apart, and are connected to the same signal. A listener is two metres away from the left speaker on a line which is perpendicular to the line joining the two speakers (see above diagram). Speed of sound in air 340m/s.

    a) When both speakers generate a 1000Hz signal what is the phase difference between them?


    Sorry if working is hard to follow having been typed up.

    Path difference = √12 + √22 = √5

    Wavelength = speed/frequency = 340/1000 = 0.34

    Using this equation ∅=2πX/wavelength,
    (2xπx√5)/0.34 = 41.32243959

    The actual answer is 4.435π Radians - can someone please explain where I went wrong?
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    I think X is meant to be "difference in path"... i.e., √(5)-2.

    But that still gives the wrong answer (1.389π)
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    (Original post by Qwertish)
    I think X is meant to be "difference in path"... i.e., √(5)-2.

    But that still gives the wrong answer (1.389π)
    I think you were right... all the possible answers look wrong to me.

    4.435 is close... 4.435 pi is miles out - why greater than 2pi?
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    (Original post by Joinedup)
    I think you were right... all the possible answers look wrong to me.

    4.435 is close... 4.435 pi is miles out - why greater than 2pi?
    Oh yes, you're right... I didn't notice that , phase difference can't be greater than 2pi... haha

    So the answer would be 1.389π, except they did 1.389π2 in the answers for some reason lol
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    (Original post by Qwertish)
    I think X is meant to be "difference in path"... i.e., √(5)-2.

    But that still gives the wrong answer (1.389π)

    (Original post by Qwertish)
    Oh yes, you're right... I didn't notice that , phase difference can't be greater than 2pi... haha

    So the answer would be 1.389π, except they did 1.389π2 in the answers for some reason lol
    Thanks so much to both of you, but 1.389π isn't an option though? Or have they made a mistake?

    also, where did the "-2" come from?

    And Qwertish, what do you mean by "except they did 1.389π2 in the answers for some reason"
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    1.389 pi = 4.364

    I think they put the pi in the multi choice by mistake
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    (Original post by Ketchup!)
    Thanks so much to both of you, but 1.389π isn't an option though? Or have they made a mistake?

    also, where did the "-2" come from?

    And Qwertish, what do you mean by "except they did 1.389π2 in the answers for some reason"
    The '-2' is the 2m of the straight path, because X is the difference between the two paths .

    I meant:
    The answer they wrote is "4.435π Radians", except the actual answer just "4.435 Radians", without the pi. So, they must have made a mistake and done 1.389π2, which simplifies to 4.435π :P.
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    (Original post by Joinedup)
    1.389 pi = 4.364

    I think they put the pi in the multi choice by mistake

    (Original post by Qwertish)
    The '-2' is the 2m of the straight path, because X is the difference between the two paths .

    I meant:
    The answer they wrote is "4.435π Radians", except the actual answer just "4.435 Radians", without the pi. So, they must have made a mistake and done 1.389π2, which simplifies to 4.435π :P.
    Thanks!!
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    (Original post by Ketchup!)
    Thanks!!
    No problem
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    (Original post by Qwertish)
    No problem
    I wish I could be good at physics one day

    May I also ask how part b is calculated?
    The answer is 180 degrees but converting 4.435rad = 254 degrees, and 1.389rad = 80 degrees.
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    (Original post by Ketchup!)
    I wish I could be good at physics one day

    May I also ask how part b is calculated?
    The answer is 180 degrees but converting 4.435rad = 254 degrees, and 1.389rad = 80 degrees.
    Hah, 180, really?

    That's completely wrong, lol. 180 degrees = pi radians.

    You might want to tell them


    And, your mistake wasn't that bad , it's easy to misread a formula.
 
 
 
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