Help for 2007 Science Q (1 Viewer)

[Cardea]

2007 Science exam - question 17. Can anyone explain why it's A? I would've thought that both A and B would be correct, but Help would be very much appreciated! Thanks in advance!

 

[rolror88]

I think its A because the energy of a wave is determined by the amplitude. Because in A, both the waves have the same amplitude, it's the answer?

I could be wrong though