Question

A radio station on the earth's surface emits a sinusoidal wave with average total power 50 kW (Fig. 32.19). Assuming that the trans- mitter radiates equally in all directions above the ground (which is unlikely in real situations), find the electric-field and magnetic field amplitudes Emax and Bmar detected by a satellite 100 km from the antenna 32.19 A radio station radiates waves into the hemisphere shown. Satellite = 100 km

Answer 1

Area, A = 2 pi r^2

A = 2 pi x 100000^2 = 6.28 x 10^10 m^2

Intensity, I = P/A

I = 50000/(6.28 x 10^10) = 7.96 x 10^-7 W/m^2

Electric field, E = sqrt(2 u0 c I)

E = sqrt(2 x 4 pi x 10^-7 x 3 x 10^8 x 7.96 x 10^-7)

E = 0.024 V/m

B)

Magnetic field, B = E/(3 x 10^8) = 8.17 x 10^-11 T

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