1. Please only answer if you KNOW the ANSWER. Its important. thanks An 800 kHz r

Question

1.

Please only answer if you KNOW the ANSWER. Its important. thanks

An 800 kHz radio signal is detected at a point 9.5 km distant from a transmitter tower. The electric field amplitude of the signal at that point is 228mV/m. Assume that the signal power is radiated uniformly in all directions and that radio waves incident upon the ground are completely absorbed. The average electromagnetic energy density at that point is closest to: 3.3 × 10-13J/m3 6.6 x 10-13/m3 9.4 x 10-13 3/m3 9.4 × 10-13J/m3 4.7 x 10-13 J/m3 4.7 × 10-13J/m3 2.3×10-13J/m3

Explanation / Answer

1. I = Em^2 / (2 c u0)

I = (228 x 10^-3)^2 / (2 x 3 x 10^8 x 4pi x 10^-7)

I = 6.89 x 10^-5 W/m^2

energy density = I / c = 2.3 x 10^-13 J/m^3

So this answer is correct.

2. f = R/2 = 60/2 = 30 cm

m = -q / p = - 1.5

q = 1.5p

1/f = 1/p + 1/q

1/30 = 1/p + 1/(1.5p)

p = 50 cm .......Ans

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