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NEET Sample Paper NEET Sample Test Paper-1

  • question_answer
    A jet plane emits sound with a frequency 990 cycles/sound and carries on board a source of light emitting radiation of wavelength\[4500\overset{o}{\mathop{A}}\,\]. If the jet plane approaches the airport with the velocity 1080 &/n/hour, then the frequency of sound beared by the observer on airport will be:

    A)  \[11890\text{ }cycles/sec.\]  

    B)  \[10890\text{ }cycles/sec.\]

    C)  \[12890\text{ }cycles/sec.\]

    D)  none of these             

    Correct Answer: B

    Solution :

    The source of approaching the observer. Hence, the observed frequency is given by \[n'=\left( \frac{V}{V-{{V}_{s}}} \right)\,n\]                ?..(i)                Here,         \[V=330m/s\]                 \[{{V}_{g}}=1080km\,h=1080\times \frac{5}{18}\]                 \[=300\,m/s\]                 \[n=990/\sec .\] from equation (i) we get                         \[n'=\left( \frac{330}{330-300} \right)\times 990\]                         \[=10890\text{ }cycles/sec\] Thus, the frequency beared by the observer is \[=10890\text{ }cycles/sec\].


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