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ID: 2266277 • Letter: W
Question
wy you ehoose that cireun vosr hand ww they didr't malch w that al Problem 5 A radio system is used to communicate with submerged operates at a frequency of 20 KHz and produces an electric field amplitude of Es V/m, on the air immediately above the surface of the sce underneath wiicinface, submarine is. Assuming that Ei is a plane wave propagating norn provide answers to the following questions: submarines. Its transmitter 100 the air-sea interface, a) Determine the intrinsic characteristic impedances of the air and the sea, and m, respectively b) How much power (in Watts per meter square) does the transmitter shines at the sea surface? c) How much power (in Watts per meter square) goes into the sea? d) If for good quality communication the submarine receiver requires an electric feld amplitude Et = 1/m, determine the largest possible depth h it has to m.aintain in order to be able to receive the transmitter message. At 20 KHz the sea water has e = 8160, -0, and = 4S/rn.Explanation / Answer
Answer:
(a) The intrinsic characteristic impedance of air and sea is given by : |E| / |H| where |E| and |H| are magnitudes of electric and magnetic fields respectively.
(b) Power shined by the transmitter = Voltage*Current
(c) Power going into the sea = Energy/time, where energy is in Joules and time is in seconds.
(d) Very low frequency EM waves (3-29 kHz) can penetrate water upto 20 meters on an average. So the submarine has to be at a depth of 20 meters to receive transmitter message successfully.
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