JEE Main & Advanced Physics EM Waves JEE PYQ-Electro Magnetic Waves

  • question_answer
    An electromagnetic wave with frequency co and wavelength \[\lambda \]travels in the + y direction. Its magnetic field is along + x-axis. The vector equation for the associated electric field (of amplitude \[{{E}_{0}}\]) is        [JEE ONLINE 19-05-2012]

    A) \[\overset{\to }{\mathop{E}}\,=-{{E}_{0}}\cos \left( \omega t+\frac{2\pi }{\lambda }y \right)\hat{x}\]

    B) \[\overset{\to }{\mathop{E}}\,={{E}_{0}}\cos \left( \omega t-\frac{2\pi }{\lambda }y \right)\hat{x}\]

    C) \[\overset{\to }{\mathop{E}}\,={{E}_{0}}\cos \left( \omega t-\frac{2\pi }{\lambda }y \right)\hat{z}\]

    D) \[\overset{\to }{\mathop{E}}\,=-{{E}_{0}}\cos \left( \omega t+\frac{2\pi }{\lambda }y \right)\hat{z}\]

    Correct Answer: C

    Solution :

    [c] In an electromagnetic wave electric field and magnetic field are perpendicular to the direction of propagation of wave. The vector equation for the electric field is
    \[\vec{E}={{E}_{0}}\cos \left( \omega t-\frac{2\pi }{\lambda }y \right)\hat{z}\]


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