The magnetic field in a plane electromagnetic wave is given by

B = (200 μT) sin [(4.0 × 1015 s–1) (t –x/c)].


Find the maximum electric field and the average energy density corresponding to the electric field.


Given: The equation of magnetic field of a plane electromagnetic


wave


B = (200 μT) sin [(4.0 × 1015 s–1) (t –x/c)]


where the amplitude of magnetic field is .


The amplitude of the electric field is related with amplitude of


magnetic field as



where C is the speed of light in free space and E0 is the amplitude


of electric field.


Thus the electric field intensity is given as





The energy density associated with an electric field is given as



where Ud is the energy density, ϵ0 is the electric permittivity of free space(vacuum) and is equal to 8.85 × 10-12 C2 N-1 m-2 and E0 is the amplitude of electric field.


Thus the electric field energy density is given by






The maximum electric field is and the corresponding


electric field energy density is .


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