Constructive Interference
Reference from the original Physics I textbook.
- Constructive Interference
Constructive interference occurs when overlapping disturbances reinforce one another. For two sinusoidal waves in phase, the resultant amplitude is A₁ + A₂.

- Related Glossary Terms
Destructive Interferenceⓘ, Two Wave Interference Equation, Wave Interference Equation, Waves with Equal Amplitude and Angular Frequency
- Index
Reviewed physics notes (1)
These corrections keep the original lesson’s purpose while fixing errors in the source edition.
- Interference combines displacement at each point; in-phase amplitudes add. — Reference 1
Glossary and deeper reading · 2 refreshers
These editorial refreshers supplement the reading. Definitions and examples are added guidance; original source wording and recorded answers remain in their original context.
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Constructive interference
Constructive interference occurs when overlapping wave contributions reinforce one another. For equal-frequency sinusoidal waves, in-phase contributions produce increased amplitude at the location considered. For example, coherent light arriving with an integer-wavelength path difference can form a bright interference fringe.
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Destructive interference
Destructive interference occurs when overlapping wave contributions oppose one another. Complete cancellation requires equal-magnitude opposite disturbances at the relevant place and time. For example, equal sinusoidal waves half a cycle out of phase can produce zero net displacement during their overlap.