Q7 of 805 Page 1

The magnetic field in a plane electromagnetic wave is given by:

By = 12 × 10–8 sin (1.20 × 107 z + 3.60 × 1015 t) T. Calculate the


(i) Energy density associated with the Electromagnetic wave


(ii) Speed of the wave

Given :


a) Magnetic field in a plane electromagnetic wave


By = 12 × 10–8 sin (1.20 × 107 z + 3.60 × 1015 t) T


The total energy density (η) = B02 /2μ0


= (12 × 10-8)2/2μ0


Here μ0 = 4π × 10-7


Therefore η =


b) B = B0 Sin(kz + ωt)


Speed =


The speed of the electromagnetic wave is 3 × 108 m/s


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