RAJASTHAN ­ PET Rajasthan PET Solved Paper-2009

  • question_answer
    Two waves are represent by \[{{y}_{1}}=A\sin (kx-\omega t)\,and\,{{y}_{2}}=A\cos \,(kx-\omega t)\] The amplitude of resultant wave is

    A)  4A               

    B)  2A

    C)  \[\sqrt{2}A\]             

    D)  A

    Correct Answer: C

    Solution :

     Given, \[{{y}_{1}}=A\sin (kx-\omega t)\] \[{{y}_{2}}=A\cos (kx-\omega t)\] or     \[{{y}_{2}}=A\sin \left( kx-\omega t+\frac{\pi }{2} \right)\] Phase difference of two waves \[=\frac{\pi }{2}\] \[\therefore \]Resultant amplitude \[R=\sqrt{{{A}^{2}}+{{A}^{2}}+2AA\cos \phi }\] \[=\sqrt{{{A}^{2}}+{{A}^{2}}+2{{A}^{2}}\cos \frac{\pi }{2}}\] \[=\sqrt{2{{A}^{2}}}\]    \[\left( \because \cos \frac{\pi }{2}=0 \right)\] \[R=\sqrt{2}A\]


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