Diffraction and Interference (Sound)
Discussion
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Nodal lines are hyperbolas. Think about it, the definition of a hyperbola is the locus of all points whose distance to two fixed points have a constant difference. At distances much greater than the wavelength, the nodal lines appear as straight radial lines.
Path length difference
| constructive | destructive |
|---|---|
| nλ = ∆ℓ | (n + ½)λ = ∆ℓ |
General equation
| constructive | destructive |
|---|---|
| nλ = d sin θ | (n + ½)λ = d sin θ |
Small angle approximation
| constructive | destructive | ||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|
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|
where…
n = 0, 1, 2, 3, …
is the order
Other Stuff
- Fringes are interference in space. (Beats are interference in time.)