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JEE Main & Advanced Physics Wave Optics / तरंग प्रकाशिकी Question Bank Wave Nature and Interference of Light

  • question_answer
    Two beams of light having intensities I and 4I interfere to produce a fringe pattern on a screen. The phase difference between the beams is \[\frac{\pi }{2}\] at point A and p at point B. Then the difference between the resultant intensities at A and B is  [IIT JEE (Screening) 2001]

    A)            2I   

    B)            4I

    C)            5I   

    D)            7I

    Correct Answer: B

    Solution :

                       At point A, resultant intensity                    \[{{I}_{A}}={{I}_{1}}+{{I}_{2}}=5I;\]and at point B                    \[{{I}_{B}}={{I}_{1}}+{{I}_{2}}+2\sqrt{{{I}_{1}}{{I}_{2}}}\cos \pi =5I+4I\]            \[{{I}_{B}}=9I\] so \[{{I}_{B}}-{{I}_{A}}=4I.\]


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