JCECE Engineering JCECE Engineering Solved Paper-2006

  • question_answer
    If ratio of intensities of interfering waves is \[16:9\], then ratio of maximum to minimum intensity is:

    A) \[49:1\]                               

    B) \[225:81\]

    C) \[3:1\]                                  

    D) \[9:1\]

    Correct Answer: A

    Solution :

    Key Idea: \[Intensity\propto {{(amplitude)}^{2}}.\] We know that                      \[I=k{{a}^{2}}\] where \[a\] is amplitude and \[I\] the intensity                 \[\frac{{{I}_{\max }}}{{{I}_{\min }}}=\frac{{{({{a}_{1}}+{{a}_{2}})}^{2}}}{{{({{a}_{1}}-{{a}_{2}})}^{2}}}\] Given,      \[\frac{{{I}_{1}}}{{{I}_{2}}}=\frac{16}{9}=\frac{a_{1}^{2}}{a_{2}^{2}}\] \[\Rightarrow \]               \[\frac{{{a}_{1}}}{{{a}_{2}}}=\frac{4}{3}\] \[\therefore \]       \[\frac{{{I}_{\max }}}{{{I}_{\min }}}=\frac{{{(4+3)}^{2}}}{{{(4-3)}^{2}}}=\frac{{{7}^{2}}}{1}=\frac{49}{1}\]


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