JEE Main & Advanced Sample Paper JEE Main - Mock Test - 4

  • question_answer
    An electromagnetic wave of frequency \[v=3.0\text{ }MHz\] passes from vacuum into a dielectric medium with relative permittivity\[{{\varepsilon }_{r}}\]. Then                                  

    A) wavelength is doubled and the frequency remains unchanged

    B) wavelength is doubled and frequency becomes half

    C) wavelength is halved and frequency remains unchanged

    D) wavelength and frequency both remains unchanged

    Correct Answer: C

    Solution :

    Refractive index \[=\sqrt{\frac{\mu \varepsilon }{{{\mu }_{0}}{{\varepsilon }_{0}}}}\]
    Here \[\mu ,\] is not specified so we can consider \[\mu ={{\mu }_{0}}\]then refractive index \[=\sqrt{\frac{\varepsilon }{{{\varepsilon }_{0}}}}=2\]
    \[\therefore \] Speed and wavelength of wave becomes half and frequency remain unchanged.       


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