WBCHSE Class 12 Physics Communication System Short Answer Questions

WBCHSE Class 12 Physics Communication System Short Question And Answers

Question 1. Why is satellite used for TV transmission to far places?
Answer:

The ionosphere is unable to reflect the signals above 40 MHz. TV signals have a frequency range of 100 MHz to 200 MHz. So TV signals are not properly reflected by the ionosphere.

So satellites are used for TV transmission to far places. Also, a communication satellite has an amplifier and transmitter that work with solar energy. The satellite amplifies the weak TV signals sent to it from the ground stations and then transmits them to the different ground stations from where they are relayed

Question 2. Write down different modes by which electromagnetic waves, can propagate from transmitting to receiving antenna. Mention one important use of the microwave.
Answer:

Electromagnetic waves propagate through the atmosphere V from the transmitting antenna to the receiving antenna in the form of ground waves, space waves, and sky waves. One important use of microwaves is communication through artificial satellites.

Practice Short Questions on Signal Types

Question 3. Draw a neat diagram of the amplitude-modulated waveform. Write down the expression’ modulation index’ and show each term in the diagram
Answer:

Modulation index, β =  \(k \frac{v_0}{V_0}\)

k = is constant

Question 4. What is the importance of the modulation index?
Answer:

The degree of modulation or modulation index is an indication of the strength of the message signal, i.e., the greater the modulation index, the stronger and clearer will be the message signal.

Question 5. In the given block diagram of a receiver, identify the boxes labelled as X and Y and write their functions.

Answer:

X is the IF block which converts the carrier frequency to a lower value and Y is the amplifier

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WBBSE Class 12 Communication System Short Q&A

Question 6. Write the function of the following in communication, and distinguish between the ‘sky wave’ and ‘space wave’ modes of the system:
Answer:

1. Transmitter: A device that transmits a suitably designed modulated signal to long distances in the form of electromagnetic wave

2. Modulator: A device that superimposes a data signal on a suitable carrier wave.

Question 7. Write two basic modes of communication.
Answer:

1. Point-to-point communication: This communication takes place over a link between a single transmitter and a receiver. Example—telephonic communication.
2. Broadcast: In Broadcast mode, there are a large number of receivers corresponding to a single transmitter. Example—radio, television

Question 8. Write the function of the following in the communication system:
Answer:

The following in the communication system:

1. Receiver
2. Demodulator

1. Receiver: A device that accepts, electromagnetic waves transmitted from distant stations, through an antenna and then sends it to the demodulator.

2. Demodulator: A device that separates, at the receiving end, a data signal from the modulated signal transmitted from distant stations

Short Answer Questions on Modulation Techniques

Question 9. Write the function of a transducer in communication
Answer:

A transducer is any device that converts one form of energy into another. In a communication system, the transducer in the receiver converts the signal into sound waves

Question 10. Why is the sky wave mode of propagation restricted to frequencies up to 40 MHz
Answer:

The sky wave mode of propagation is ionospheric propagation. In the frequency range from a few MHz up to 30MHz to 40 MHz, long-distance communication can be achieved by ionospheric reflection of radio waves back toward the earth. Hence, the sky wave mode of propagation is restricted to frequencies up to 40 MHz