Question

The process of superimposing message signal on high frequency carrier wave is called
(A) Amplification
(B) Demodulation
(C) Transmission
(D) Modulation

Answer 1

Hint We will see that there are two types of waves for carrying out communication. These are signal waves and carrier waves. We will see that when a signal wave was superimposed on a high frequency carrier wave then it is known as modulation.

Complete step by step solution:
Amplification: it means increase in amplitude of waves. DC signal gets converted into AC signal.
Demodulation: it is an electronic device which is used to extract signal from a carrier wave. Initial input signal gets recovered.
Transmission: waves are propagated from one point to the other. Signals sent from the sender are encoded which are transmitted to the receiver which decodes it. Encoding and decoding are done via this line.
Modulation: Manipulating carrier signal. Frequency, phase and transposition modulation takes place. In this case the frequency of carrier signal is altered. So, it is the case of modulation. Since modulation is taking place, option D is the correct solution.

Therefore, option D is the correct option.

Note:
If the phase of the carrier wave would have altered then also modulation would be the correct solution. If the amplitude of the wave is increased then the solution would be part A I.e. amplification. but it is not taking place so it is a wrong option. If waves propagate from a point and end at the other then transmission would be taking place but it is not so it is again a wrong option. If we are getting a signal wave from a carrier wave then demodulation would have been occurring but it is not happening so it is a wrong option.