A) Short waves are completely absorbed by ionosphere.
B) Radio waves are unpolarised electromagnetic waves.
C) Optical interference between fibres is zero.
D) Shorter the wavelength, the smaller is the velocity of wave propagation.
Correct Answer: C
Solution :
[c] It is true the radio waves are polarized electromagnetic waves. The antenna of portable AM radio is sensitive to only magnetic components of electromagnetic waves. On account of this the set should be put horizontal and in proper situation so that the signals are received properly from radio station. Optical communication is a system by which we transfer the in formations over any distance from one location to other through optical range of frequency using optical fibre. The optical interference between fibres is zero. Hence, optical fibre communication has immunity to cross talk. The electromagnetic waves of shorter wavelength do not suffer much diffraction from the obstacles of earth's atmosphere so they can travel long distance. Also, shorter the wavelength, shorter is the velocity of wave propagation.
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