An electromagnetic wave travelling in a lossless dielectric medium having a dielectric constant, _r=9, has the electric field, E_x=E_0 (kz-2 10^6 t) Vm^ -1 where E_0 is the amplitude and k is the wave vector. Among the following options, the incorrect choice is :
C. The wavelength of the electromagnetic wave inside the medium is 300 m
From the given equation of the electric field E_x = E_0 (kz - 2 10^6 t), the wave is propagating in the +z direction. The angular frequency is = 2 10^6 rad/s, which gives the frequency f = 2 = 10^6 Hz. The speed of the electromagnetic wave in the dielectric medium is given by v = c _r _r . Assuming a non-magnetic medium ( _r = 1), we get v = 3 10^8 9 = 10^8 ms^ -1 . The wavelength of the wave inside the medium is = v f = 10^8 10^6 = 100 m. Option (3) states the wavelength is 300 m, which is incorrect.
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