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JEE Main & Advanced Sample Paper JEE Main - Mock Test - 26

  • question_answer
    A plane electromagnetic wave is incident on a plane surface of area A, normally and is perfectly reflected. If energy E strikes the surface in time t then average pressure exerted on the surface is \[\left( c = speed of light \right)\]

    A) zero                              

    B)        E/Atc

    C)        2E/Atc              

    D)        E/c

    Correct Answer: C

    Solution :

    Incident momentum, \[\operatorname{p} =\frac{E}{e}\] For perfectly reflecting surface with normal incidence \[\Delta p=2p=\frac{2E}{c}\] \[F=\frac{\Delta p}{\Delta t}=\frac{2E}{ct}\] \[P=\frac{F}{A}=\frac{2E}{ct\,A}\]


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