Concept:Interference is dictated by the precise alignment of superimposing waves, measured by their phase difference.
Solution:- Constructive interference happens when crests perfectly align with crests (in-phase, or \( 0^\circ \) difference).
- Destructive interference requires maximum cancellation. This happens only when the crest of wave A perfectly aligns with the trough of wave B.
- To shift a wave so its crest becomes a trough, it must be shifted by half a cycle.
- Half of a full cycle (\( 360^\circ \)) is exactly \( 180^\circ \) (or \( \pi \) radians).
Why other options are incorrect:\( 0^\circ \) causes pure constructive interference. \( 90^\circ \) or \( 45^\circ \) cause complex partial interference, but not complete destructive cancellation.
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