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BCECE Engineering BCECE Engineering Solved Paper-2010

  • question_answer
    A source emits electromagnetic waves of wavelength 3 m. One beam reaches the observer directly and other after reflection from a water surface, travelling 1.5 m extra distance and with intensity reduced to (1/4) as compared to intensity due to direct beam alone. The resultant intensity will be

    A)  (1/4) fold                           

    B)  (3/4) fold

    C)  (5/4) fold           

    D)         (9/4) fold

    Correct Answer: D

    Solution :

    Two waves superimpose in phase. Hence, resultant amplitude \[=\sqrt{I}+\sqrt{I/4}=\frac{3}{2}\sqrt{I}\] So, resultant intensity \[={{\left( \frac{3}{2}\sqrt{I} \right)}^{2}}=\frac{9}{4}I=\frac{9}{4}\]fold


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