Final answer:
The statement regarding the observed frequency becoming infinite at the speed of sound is false. The correct explanation involves the Doppler effect and the compression of sound waves, which do not result in an infinite frequency.
Step-by-step explanation:
The statement that the observed frequency becomes infinite when the source is moving at the speed of sound is false. This concept is related to the Doppler effect, which describes the change in frequency or wavelength of a wave in relation to an observer who is moving relative to the wave source. However, when the source moves at the speed of sound, the waves pile up and create a shock wave, such as a sonic boom, but they do not produce an infinite frequency. As the source approaches the speed of sound, the frequency increases, but it does not become infinite. When a source moves at the speed of sound, the frequencies from the source are compressed, but due to the finite speed of sound, the frequency does not reach infinity