Final answer:
The observed frequency does not become infinite when the source is moving at the speed of sound.
Step-by-step explanation:
The correct answer is False. The observed frequency does not become infinite when the source is moving at the speed of sound. This concept relates to the Doppler effect, which describes the change in frequency or wavelength of a wave due to the relative motion between the source and observer. When a source is moving at the speed of sound, it creates a shockwave known as a sonic boom, which is characterized by a sudden and intense increase in pressure. However, the observed frequency does not become infinite.