Final answer:
The statement about interference types is true: constructive and destructive interference are the two types. The external force definition as one originating outside the system and acting within it is also true. However, wave amplitudes can influence each other without precise alignment, making that statement false.
Step-by-step explanation:
Wave Interference Types
The statement that the two types of interference are constructive and destructive interferences is true. In wave physics, when two waves meet, they superimpose on each other, creating either an increased amplitude (constructive interference) if their peaks align, or a decreased amplitude (destructive interference) if a peak aligns with a trough of the other wave.
External Force Definition
An external force is indeed defined as a force that is applied from outside the system of interest and affects an object within the system. Therefore, the statement is true.
Wave Amplitude Influence
The amplitude of one wave affecting the amplitude of another wave occurs during wave interference, and it does not require the waves to be 'precisely aligned' for this to happen. Amplitude affects can occur even when waves partly overlap. Thus, this statement is false.