Constructive interference occurs when peaks align with peaks and troughs align with troughs. This results in:

Constructive interference occurs when peaks align with peaks and troughs align with troughs. This results in:

• A. Peaks align with peaks and troughs align with troughs.
• B. Peaks align with troughs.
• C. Peak alignment is unrelated to interference.
• D. Frequencies must be different.

Answer: (A)

When waves are in phase, their peaks line up with peaks and their troughs line up with troughs, so their displacements add together rather than cancel. This in-phase alignment is what creates constructive interference, producing a larger resultant wave and greater intensity at the overlap. If the amplitudes are equal, the peak can reach about twice as high as either wave alone, and the overall energy concentrates where they reinforce. So describing the condition as peaks aligning with peaks and troughs aligning with troughs directly captures why constructive interference occurs. Conversely, peaks meeting troughs would cancel (destructive interference), and differing frequencies would cause the phase relationship to drift, leading to beating rather than a steady constructive result.