In analog modulation, which of the following changes proportionally to an incoming analog signal?

In the context of analog modulation, the correct answer involves understanding how the characteristics of a carrier wave are altered in response to an incoming analog signal. When using analog modulation techniques such as amplitude modulation (AM), the amplitude of the carrier wave is varied in proportion to the instantaneous amplitude of the incoming analog signal.

Thus, the intensity of the signal relates directly to the incoming modulation, which represents the signal's information content. As the amplitude of the incoming analog signal increases or decreases, the amplitude of the modulated carrier wave changes correspondingly. This modulation technique allows for the transmission of information over radio waves or other communication channels by varying the strength (intensity) of the carrier wave.

In contrast, frequency and phase modulation operate differently. In frequency modulation, the frequency of the carrier wave changes in response to the incoming signal, not the amplitude. Similarly, in phase modulation, it is the phase of the carrier that is varied with respect to the incoming signal. Understanding these differences clarifies why intensity, or amplitude, is the appropriate choice in this scenario for analog modulation.