Final answer:
When the sonographer increases the output gain, the intensity of the ultrasound wave increases. This is due to an increase in power, which is related to the square of the wave's amplitude.
Step-by-step explanation:
The component of the ultrasound wave that increases when the sonographer increases the output gain is the intensity of the wave. Intensity is related to the power carried by the wave and is proportional to the square of the amplitude. When the output gain is increased, the power of the ultrasound wave increases, leading to an increase in its intensity, not the frequency, pulse duration, or noise. This concept is similar to increasing the loudness of sound, where the amplitude of the wave increases.