Question

Amplitude of resultant wave formula from displacement equation

Answer 1

If two identical waves are traveling in the same direction, with the same frequency, wavelength and amplitude; BUT differ in phase the waves add together. When φ = 0 (crest to crest and trough to trough), then cos (φ /2) = 1. resultant wave is A1 + A2 = 2A. The waves are “in phase.”