VIT Engineering VIT Engineering Solved Paper-2007

  • question_answer
    Pour independent waves are represented by equations: (1) \[{{X}_{1}}={{a}_{1}}\,\sin \,\omega t\] (2) \[{{X}_{2}}={{a}_{1}}\,\sin \,2\omega t\] (3) \[{{X}_{3}}={{a}_{1}}\,\sin \,{{\omega }_{1}}t\] (4) \[{{X}_{4}}={{a}_{1}}\,\sin \,\left( \omega t+\delta  \right)\] Interference is possible between waves represented by equations:

    A)  3 and 4

    B)  1 and 2

    C)  2 and 3        

    D)  1 and 4

    Correct Answer: D

    Solution :

    To see interference, we need two sources with the same frequency and with a constant phase difference. In the given waves, \[{{X}_{1}}={{a}_{1}}\,\sin \,\omega t\] and        \[{{X}_{4}}={{a}_{1}}\,\sin \,(\omega t+\delta )\] have a constant phase difference \[\delta ,\]  so interference is possible between them. For         \[{{X}_{1}}={{a}_{1}}\,\,\sin \,\,\omega t,\] and        \[{{X}_{2}}={{a}_{2}}\,\,\sin \,2\omega t,\] frequency is not equal and there is no constant phase difference. For          \[{{X}_{1}}={{a}_{1}}\,\sin \,\,\omega t,\] and        \[{{X}_{3}}={{a}_{1}}\,\sin \,\,{{\omega }_{1}}t,\] frequency is different and there is no constant phase difference.


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