The electric-field phasor of a uniform plane wave traveling downward in water is given by ...

The electric-field phasor of a uniform plane wave traveling downward in water is given by

where is the downward direction and z = 0 is the water surface. If σ = 4 S/m,

(a) Obtain an expression for the average power density.

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(b) Determine the attenuation rate.

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(c) Determine the depth at which the power density has been reduced by 40 dB.