To cause two waves to interfere completely destructively they have to

A) *have the same amplitude
B) *be exactly out of phase
C) *one wave's peak must align with the other's valley
D) *be transverse waves
E) *all of the above

which of these statements apply? (can be as more than one)

A), B) and C),

- To be completely destructive, they must have the same amplitude or there will be some "residue" if you will.
- They must be out of phase. Imagine two added vectors x and y, the only way for the result to equal zero is if x = -y. Now imagine a straight line (an infinite number of points) with a horizontal vector both over and beneath each point. The only way for it to remain a straight line is if these vectors are both equal and opposite, and the only way for the to happen is if it's out of phase.
- A repetition B), but also technically correct.

A), B) and C).

MW

Must be of same amplitude and the phase difference must be 180 degrees
A AND C satisfy the requirements.

"Exactly out of phase" is about as clear as "slightly pregnant".

A) & B) is the answer

E. All the above

A and C,
IVAN