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JEE Main & Advanced Sample Paper JEE Main - Mock Test - 40

  • question_answer
    Two waves \[{{y}_{1}}=A\,cos\left( 0.5\pi x-100\pi t \right)\] and \[{{y}_{2}}=A\,cos\left( 0.46\pi x-92\pi t \right)\] are travelling in a pipe along x-axis. (y and x are in metre). How many times in a second does a stationary any observer hear loud sound (maximum intensity)?

    A) 4         

    B) 8     

    C) 10                    

    D)        12

    Correct Answer: A

    Solution :

    [a] Hence \[{{\omega }_{1}}=100\pi \] and \[{{\omega }_{2}}=92\pi \]s Hence \[{{V}_{1}}=\frac{100\pi }{2\pi }=50\,Hz\] And \[{{V}_{2}}=\frac{92\pi }{2\pi }=46\,Hz\] \[\therefore \] Number of beats per second \[={{V}_{1}}-{{V}_{2}}\] \[=50-46=4\]    


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