CBSE Class 12-science Answered

The information or message signal are also called as base band signal. In general, it spreads over a range of frequencies called the signal bandwidth.

(i)  For speech signals, frequency range is from 300 Hz to 3100 Hz at the maximum end. Hence the bandwidth of speech signals = 3100 Hz - 300 Hz = 2800 Hz.

(ii) Different musical instruments produce high frequencies covering the entire range of audible frequencies from 20 Hz to 20 kHz. Hence, a bandwidth of about 20 kHz is required for music signal.

(iii) Video signals require about 4.2 MHz of bandwidth. As TV signals contain both video as well as voice, hence a signal band width of 4.5 MHz is required. But to avoid interference among telecast by different TV stations, a TV channel is usually allotted 6 MHz of bandwidth for transmission.