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JEE Main & Advanced Physics Wave Mechanics Question Bank Mock Test - Waves and Acoustics

  • question_answer
    Vibrating tuning fork of frequency n is placed near the open end of a long cylindrical tube. The tube has a side opening and is fitted with a movable reflecting piston. As the piston is moved through   8.75 cm, the intensity of sound changes from a maximum to minimum. If the speed of sound is 350 m/s. Then n is

    A) 500 Hz 

    B) 1000 Hz

    C) 2000 Hz

    D) 4000 Hz

    Correct Answer: B

    Solution :

    [b] When the piston is moved through a distance of 8.75 cm, the path difference produced is \[2\times 8.75\] cm = 17.5 cm. This must be equal to\[\frac{\lambda }{2}\] for maximum to change to minimum. \[\therefore \frac{\lambda }{2}=17.5cm\Rightarrow \lambda =35cm=0.35cm\] So, \[v=n\lambda \Rightarrow n=\frac{v}{\lambda }=\frac{350}{0.35}=1000Hz\]


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