Final answer:
The statement about the two types of interference being constructive and destructive is true, while the statement that the observed frequency becomes infinite at the speed of sound is false.
Step-by-step explanation:
Wave Interference and Doppler Effect
For your question regarding wave interference: The statement that the two types of interference are constructive and destructive interference is true. Constructive interference occurs when waves add together, which can lead to a larger amplitude. On the other hand, destructive interference occurs when waves subtract from each other, leading to a smaller amplitude or even cancelation of the waves.
As for the observed frequency and the speed of sound: The statement that the observed frequency becomes infinite when the source is moving at the speed of sound is false. When the source moves at the speed of sound, a phenomenon known as the sonic boom occurs, but the frequency does not become infinite; instead, the waves pile up and create a sharp increase in pressure.