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Physics Pre answers anyone??

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  • 14-06-2008 3:06pm
    #1
    A-Bit-Dodge
    Registered Users Posts: 152 ✭✭


    I think there was only one but could anyone that got the first part of the sound question please PLEASEE help me out here...

    A loudspeaker produces a sound of frequency 820 Hz.
    The sound is reflected off the wall B.

    As an observer moves from A to B it is noticed that the sound becomes louder and quieter in a regular manner.
    State the type of wave that is formed between A and B and explain how this wave is formed.

    WTF?? Is it coherent sources, destructive/constructive interference, I havent a clue!!! And its really bugging me..


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    #2
    starkinter
    Closed Accounts Posts: 59 ✭✭starkinter


    It's a standing/stationary wave, caused by the original wave and reflected wave (both of equal amplitude and frequency) combining.


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    #3
    A-Bit-Dodge
    Registered Users Posts: 152 ✭✭A-Bit-Dodge


    starkinter wrote: »
    It's a standing/stationary wave, caused by the original wave and reflected wave (both of equal amplitude and frequency) combining.



    You're a genius!!! ;)


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    #4
    Peleus
    Registered Users Posts: 784 ✭✭✭Peleus


    it gets louder and quieter because hes going from nodes to antinodes i think.


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    #5
    The LeavyC
    Closed Accounts Posts: 50 ✭✭The LeavyC


    coherent sources are sources that are in phase or have a regular phase difference. interference is kind of hard to describe without a diagram but,

    Destructive interference is when the waves coming from the sources combine to negate each other. this is because they are at opposite parts of the wave motion, ones going up and ones going down so they collide head on and cancel each other. their amplitudes cancel out. A1 - A2 = 0


    Constructive interference is when the waves coming from the sources combine to amplify the wave. this is because they are at the same part of the wave motion, both are going up or both going down, so they join together and make a bigger amplitude. their amplitudes are added. A1 + A2 = new A


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