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Question
In Young’s double slit experiment, what should be the phase difference between the two overlapping waves to obtain 5th dark band/fringe on the screen?
Solution
For dark band path difference
P = (2m - 1)`lambda/2`
Here m = 5
P = `(2 xx 5 - 1)lambda/2 = (9lambda)/2`
∴ Phase difference = `(2pi)/lambda xx "p"`
`= (cancel(2)pi)/cancel(lambda) xx (9cancel(lambda))/cancel(2)`
= 9 π
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