JAMIA MILLIA ISLAMIA Jamia Millia Islamia Solved Paper-2007

  • question_answer
        An electromagnetic wave of frequency \[v=3.0\text{ }MHz\]passes from vacuum into a dielectric medium with permittivity\[\varepsilon =4.0\]. 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 remain unchanged

    Correct Answer: C

    Solution :

                    In vacuum, \[{{\varepsilon }_{0}}=1\] In medium, \[\varepsilon =4\] So, refractive index                                 \[\mu =\sqrt{\varepsilon /{{\varepsilon }_{0}}}\]                                 \[=\sqrt{4/1}=2\] Wavelength       \[\lambda =\frac{\lambda }{\mu }=\frac{\lambda }{2}\] and wave velocity\[v=\frac{x}{\mu }=\frac{c}{2}\] Hence, it is clear that wavelength and velocity will become half but frequency remains unchanged when the wave is passing through any medium.


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