Modulation is the phenomenon of superimposing the low audio frequency base band message or information signals ( called the modulation signals) on a high frequency wave (called, the carrier wave). The resultant wave is called the modulated wave, which is transmitted.
Read the above passage and answer the following questions:
(i) What are the Audio Frequency and Radio Frequency ranges?
(ii) Why audio frequency signals, as such cannot be transmitted over long distance?
(iii) What does the phenomemom imply in day to day life ?

Explanation

(i) The AF range is 20 Hz to 20 kHz and RF range is `5 xx 10^5 Hz "to" 10^9 Hz.`
(ii) Audio frequency signals, as such cannot be transmitted over long distances because size of antenna required
is too large, effective power radiated is small and mixing up of signals from different transmitters causes problems.
(iii) In day to day life, modulation is so evident. For example, we cannot travel long distance on foot. We have
to travel by air or by train or by car/bus.They act as our carriers, carrying us to our destinations at long
distance