PhysicsChapter 4: Diffraction and Interference
Constructive and Destructive Interference
**Constructive interference** occurs when waves combine to produce greater amplitude, while destructive interference
Definition
Constructive interference occurs when waves combine to produce greater amplitude, while destructive interference occurs when their combination reduces the resultant amplitude.
Constructive Interference
For coherent waves: Waves arrive in phase. Phase difference: **Δφ = 2nπ Path difference: Δr = nλ where: `n = 0,1,2,...` For equal amplitudes, maximum resultant amplitude is: 2A**
Destructive Interference
Waves arrive out of phase by an odd multiple of π. Phase difference: **Δφ = (2n+1)π Path difference: Δr = (n+½)λ** For equal amplitudes, complete cancellation can occur.
Relation Between Phase and Path Difference
**Δφ = 2πΔr/λ**
Formula / Key Relation
Constructive: **Δr=nλ Destructive: Δr=(n+½)λ Phase relation: Δφ=2πΔr/λ**
Exam preparation
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Review the key facts, formulas and checks before you move on.Constructive and Destructive Interference
Sticky Notes · Quick Revision
Constructive:
- `0, λ, 2λ...`
- Destructive:
- `λ/2, 3λ/2, 5λ/2...`
60-second revision
- Interference condition depends on path difference.
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