Q.The modulation used in TV transmission is

TV transmission uses amplitude modulation (AM) for the picture/video signal and frequency modulation (FM) for the sound signal.

This question belongs to the Communication Systems chapter, which has been removed from the NCERT syllabus after the post-2023 rationalization, so it is out of the current CHSE Odisha Class-12 syllabus. It is answered here for completeness since it appeared in this PYQ paper.

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Modulation superimposes a low-frequency information signal onto a high-frequency carrier by varying the carrier's amplitude, frequency, or phase.

A low-frequency (baseband) message signal cannot be radiated efficiently over long distances - it would need impractically large antennas and would suffer poor range and interference. To overcome this, the message is impressed on a high-frequency carrier wave.

Definition: Modulation is the process in which a property of the carrier wave (amplitude, frequency, or phase) is changed in step with the instantaneous value of the message signal. Accordingly we have:

• Amplitude Modulation (AM): carrier amplitude varies with the message. …