This set of Physics Multiple Choice Questions & Answers (MCQs) focuses on “Communication Systems – Bandwidth of Signals”.
1. The communication system needed for a given signal depends on which of the following?
a) Band of frequencies
b) Length of the channel
c) Size of the transmitter
d) Size of the collector
Explanation: Each of the message signals has different ranges of frequencies. The type of communication system needed for a given signal depends on the bad of frequencies which are considered essential for the communication process.
2. What is the frequency range for a speech signal?
a) 20 Hz to 20 kHz
b) 20 kHz to 20 MHz
c) 300 Hz to 3100 Hz
d) 30 Hz to 310 Hz
Explanation: For speech signals, the frequency range of 300 Hz to 3100 Hz is considered adequate. Therefore, speech signals require a bandwidth of 2800 Hz (3100 Hz – 300 Hz) for commercial telephonic communication.
3. The frequencies for transmitting music is which of the following?
d) Very high
Explanation: To transmit music, an approximate bandwidth of 20 kHz is required because of the high frequencies produced by the musical instruments. The audible range of frequencies extends from 20 Hz to 20 kHz.
4. A TV signal is allocated with a bandwidth of 6 MHz.
Explanation: Yes, this is a true statement. Video signals for transmission of pictures require about 4.2 MHz of bandwidth. A TV signal contains both voice and picture and is usually allocated 6MHz of bandwidth for transmission.
5. Find the true statement.
a) The value of the harmonic is equal to its contribution to the waveform
b) The value of the harmonic is directly proportional to its contribution to the waveform
c) The value of the harmonic is independent of its contribution to the waveform
d) The value of the harmonic is inversely proportional to its contribution to the waveform
Explanation: When the bandwidth is large enough to accommodate a few harmonics, the information is not lost and the rectangular signal is more or less recovered. This is so because the higher the harmonic, the less is its contribution to the waveform. Therefore, the value of the harmonic is inversely proportional to its contribution to the waveform.
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