Question

Destructive interference of two waves travelling in a medium occurs when the crest of one wave lines up with the ........... of another wave.

• A. trough
• B. amplitude
• C. crest
• D. frequency
• E. wavelength

Answer 1

Answer: (A)

trough

Destructive interference occurs between two waves when they are completely out of phase to each other.
Crests and troughs are separated by a phase of ${180}^{\circ }$.

Hence if crest of a wave lines with trough of the other, they are completely out of phase and thus would result in destructive interference.