InterviewSolution
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InterviewSolution
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A plane e.m. wave travelling along the x-direction has a wavelength of 3mm. The variation in the electric field occurs in the y-direction with an amplitude `66Vm^-1`. The equation for the electric and magnetic fields as a function of x and t are respectivelyA. `E_y=33cos pixx10^(11)(t-x/c)` `B_z=1.1 xx10^-7cos pixx10^(11) (t-x/c)`B. `E_y=11cos 2pixx10^(11)(t-x/c)` `B_y=11 xx10^-7cos 2pixx10^(11) (t-x/c)`C. `E_x=33cos pixx10^(11)(t-x/c)` `B_y=11 xx10^-7cos pixx10^(11) (t-x/c)`D. `E_y=66cos pixx10^(11)(t-x/c)` `B_z=2.2 xx10^-7cos 2pixx10^(11) (t-x/c)` |
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Answer» Correct Answer - d `lambda=3mm=3xx10^-3m , E_0=66Vm^-1` `B_0=(E_0)/c =66/(3xx10^8)=2.2 xx10^-7T` As em wave is propagating along x-axis and electric field variation is along y-direction, the magnetic field variation is along z-direction. Using the relation for harmonic wave `E_y=E_0cos .(2pi)/lambda(ct-x)` `E_y=E_0cos .(2pic)/lambda(t-x/c)` `:. E_y=66cos .(2pixx3xx10^8)/(3xx10^-3)(t-x/c)` `=66 cos 2pixx10^(11)(t-x/c)` and `B_z= B_0cos .(2pic)/lambda(t-x/c)` `=2.2xx10^-7cos 2pixx10^(11)(t-x/c)` Thus, option (d) is correct. |
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