Final answer:
Many of the statements about wave behavior are true, clarifying the nature of wave interference, superposition, pulse waves, and the behavior of photoconductive cells. Some statements about precise alignment of waves and standing waves were false, and the claim about observed frequency becoming infinite at the speed of sound is also false.
Step-by-step explanation:
The statement that the amplitude of one wave is affected by the amplitude of another wave only when they are precisely aligned is false. Waves can affect each other's amplitudes through the principles of interference, which occurs even when waves are not precisely aligned. There are indeed two types of interference - constructive interference and destructive interference, and this principle is true as it relates to wave superposition.
Additionally, the statement that waves can superimpose if their frequencies are different is true. Different frequency waves can still interfere with one another to create complex wave patterns, although they won't form a stable interference pattern. As for the amplitudes of waves adding up only if they propagate in the same line, this is false because waves traveling in different directions can still affect each other when they intersect, leading to a change in amplitude.
Dropping a pebble in water creates a pulse wave, so the statement that it is an example of a pulse wave is true. Regarding photoconductive cells, it is true that a current can be created even if only one electron is expelled due to a photon strike, as this can initiate an electrical signal. The statement about a standing wave is false; standing waves are formed by the superposition of two identical waves that are traveling in opposite directions, not the same direction. Lastly, the statement that the observed frequency becomes infinite when the source is moving at the speed of sound is false; the frequency increases but does not become infinite.