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How does the path difference between two interfering waves affect the pattern of interference obtained on the screen? For a well distinguished pattern of interference(i.e., good contrast between dark and bright bands) should the path difference be large or small? Please explain
- Anu (age 17)
The path difference between two interfering waves, be they electromagnetic, sound or water, makes all the difference. Many waves can be characterized by a sinusoidal function A = sin(x/2π λ + φ) where λ is the wavelength and φ is a phase angle. If there is a path length difference then the phase angles between two waves will be different; Δφ =
Δx/2π λ where Δx is the path length difference and Δφ is the phase difference. When Δφ is a multiple of 2π then you get constructive interference. When Δφ is a multiple of 2π plus π then you get destructive interference and the total amplitude goes to zero (or close to it). The web site http://en.wikipedia.org/wiki/Interference_%28wave_propagation%29
has some nice pictures and explanations.
(published on 10/01/10)
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