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i have a doubt what is the formulae to find dark fringe is it (2n+1)LD/2d or it is (2n-1)LD/2d where L is lambda

i have a doubt


what is the formulae to find dark fringe


is it  (2n+1)LD/2d


or it is  (2n-1)LD/2d


where L is lambda 

Grade:11

3 Answers

KARAN ACHARYA
52 Points
11 years ago

both are correct but 2n-1 is preferably used

 

in the formula 2n-1  n is the position of dark fringe

 

while  for 2n+1 position of fringe is n+1

example n=0 => 2X(0) +1 =1 [1ST DARK FRINGE]

 

vijesh jayan
49 Points
11 years ago

thnk u

Mir Noaman Ali IIT-Roorkee
57 Points
11 years ago

Dear Vijesh

Both the formulae are correct, on putting n as sum integer we get two successive dark fringes by those 2 formulae 

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