How does frequency modulation (FM) differentiate from amplitude modulation (AM)?

• A. FM changes the frequency of the carrier wave, while AM changes the amplitude
• B. FM uses a single frequency, while AM uses multiple frequencies
• C. FM is used mainly for television, while AM is used for radio
• D. FM has a broader range than AM

Answer: (A)

Frequency modulation (FM) differentiates from amplitude modulation (AM) primarily by the way each type modulates the carrier wave. In FM, the frequency of the carrier wave is varied in accordance with the amplitude of the input signal. This means that the information is encoded in the frequency changes, while the amplitude remains constant. In contrast, AM varies the amplitude of the carrier wave based on the amplitude of the input signal, meaning that it encodes the information through changes in signal strength rather than frequency.

The other choices, while touching on characteristics of FM and AM, do not accurately capture the fundamental difference in modulation techniques. The claim that FM uses a single frequency while AM uses multiple frequencies does not adequately represent the nature of how these modulations work. Additionally, the assertion that FM is primarily used for television does not reflect its broader usage for certain types of radio broadcast as well. Meanwhile, while it is often true that FM can have a potentially broader range in terms of sound quality and resilience to noise, that is not the primary differentiation based on modulation technique.

Thus, the definition of FM and AM in terms of their modulation methods is crucial in discussing how they diverge from each other.