Answer;
- In phase
Step-by-step explanation;
Constructive interference occurs when the maxima of two waves add together (the two waves are in phase), so that the amplitude of the resulting wave is equal to the sum of the individual amplitudes.
Constructive interference occurs when waves come together so that they are in phase with each other. This means that their oscillations at a given point are in the same direction, the resulting amplitude at that point being much larger than the amplitude of an individual wave.
Therefore; For two waves of equal amplitude interfering constructively, the resulting amplitude is twice as large as the amplitude of an individual wave.