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The interference taking place at points of maximum intensity is called constructive interference .
The interference taking place at points of minimum intensity is destructive interference .
Fringe Width
The distance between the centres of two consecutive bright or dark fringes is called the fringe width .
The angular fringe width is given by θ = λ / d . where λ is the wavelength of light d is the distance between two coherent sources .
Conditions for Constructive and Destructive Interference For Constructive Interference
Phase difference , φ = 2nπ Path difference , Δx = nλ where , n = 0 , 1 , 2 , 3 ,…
For Destructive Interference
Phase difference , φ = ( 2n – 1 ) π Path difference , Δx = ( 2n – 1 ) π / 2 where , n = 1 , 2 , 3 , …
If two waves of exactly same frequency and of amplitude a and b interfere , then amplitude of resultant wave is given by
R = √a 2 + b 2 + 2ab cos φ where φ is the phase difference between two waves . R max = ( a + b ) R min = ( a – b )