Select the answer that best completes this sentence: In analog modulation, the ____ of the light wave changes in ____ proportion to the ____ analog signal.

In analog modulation, the intensity of the light wave changes in direct proportion to the incoming analog signal. This means that as the amplitude of the analog signal varies, the intensity of the light wave (which can be thought of as the brightness) also varies in a linear manner. If the incoming analog signal increases, the intensity of the light wave increases proportionally; if the analog signal decreases, the intensity diminishes correspondingly. This relationship is fundamental in communication systems where analog signals need to be transmitted using light waves, ensuring that the message conveyed is a faithful representation of the source signal.

In contrast, other options conceptualize changes in different characteristics of the light wave or refer to relationships that do not align with how analog modulation functions. For instance, the frequency and phase are associated with different modulation techniques and do not vary directly with analog signal amplitude in the context of analog modulation. Thus, focusing on how intensity directly reflects the changes in the incoming analog signal highlights the core principle of analog modulation effectively.