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JEE Main & Advanced Sample Paper JEE Main Sample Paper-18

  • question_answer
    A sound source is situated at the origin and is continuously emitting sound waves of frequency 660 Hz. The velocity of sound in air is 330 m/s. An observer is moving along the X = 335 m line with a constant velocity of 26 m/s. When the observer is at positions where y = -140 m, y = 0 m and y = 140 m, the frequencies of the sound observed by him will be

    A)  680 Hz, 660 Hz and 640 Hz

    B)  640 Hz, 660 Hz and 680 Hz

    C)  680 Hz, 640 Hz and 660 Hz

    D)  660 Hz, 680 Hz and 640 Hz

    Correct Answer: A

    Solution :

     at \[A,\]\[{{n}_{1}}=\frac{330+26\times \frac{140}{364}}{330}\times 660=680\,hz.\] at\[O,\]\[{{n}_{2}}=\frac{330}{330}\times 660=660\,hz\] at\[B,\]\[{{n}_{3}}=\frac{330-26\times \frac{140}{364}}{330}\times 660=640\,hz\]


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