PHYSICAL LAYER AND TRANSMISSION MEDIA
TRANSMISSION MEDIA
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Question
[CLICK ON ANY CHOICE TO KNOW THE RIGHT ANSWER]
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the troposphere
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the ionosphere
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space
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sea water
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Detailed explanation-1: -In this theory, waveguide modes are trapped between the surface of the Earth and the base of the ionosphere. Trapping occurs because the VLF electromagnetic wavelength (30km-3 km) is comparable with the 75-90 km height between the base of the ionosphere and the earth.
Detailed explanation-2: -For seawater, the conductivity is usually =4S/m and the dielectric constant =810 . When the frequency satisfies f≪887MHz, the seawater is a good conductor. The attenuation constant and the phase constant are approximately equal.
Detailed explanation-3: -Very Low Frequency (VLF) communications transmitters use digital signals to communicate with submerged submarines on at frequencies of 3-30 kHz. The eighteen Trident submarines constitute about half the US strategic nuclear capability.