Audio signals are not transmitted by EM waves because
(i) Antennas used will be unimaginably lengthy
(ii) Audio signals do not radiate
(iii) Interference is due to simultaneous transmissions.
(iv) Usable frequency range is too low and narrow. Which of the following is correct ?
UGC NET - 2013,
Answer: C
The keyed answer is statements (i) and (iii), option (C). Audio frequencies are too low to be radiated efficiently, since an antenna must be a sizeable fraction of the wavelength and would have to be unimaginably long, and if several stations sent audio directly they would interfere with each other, as they would all use the same band.
Statement (ii), that audio signals do not radiate, is not accepted as a reason. Option D adds (iv), the low and narrow usable frequency range, which the key does not accept. A reviewer may wish to check whether (iv) is also a fair reason.
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