Constructive and Destructive interference

  1. Hello guys I have a question about constructive/ destructive interference.

    I know that in single slit and double slit patterns that the
    dark fringes=destructive interference (minima)
    bright fringes = constructive interference (maxima)

    I do know that the formula's are as follows:
    Single slit:
    constructive: path differene= mlambda
    (a)sin(theta)= m lambda where m=1,2,3,4 etc...
    destructive: path difference= 1/2(m) (lambda)
    (a) sin (theta)= (m)lambda where m= 1,3,5,7 etc...

    double slit:
    constructive interfernce: path differene= mlambda
    (d)sin(theta)= m lambda where m=1,2,3,4 etc...
    destructive: path difference= 1/2(m) (lambda)
    (d) sin (theta)= (m)lambda where m= 1,3,5,7 etc...

    So yes I would like you guys to tell me if these formula's are right.... i have been looking in my notes and it really isn't clear.

    One last thing... how do you know if you have a constructive pattern or a destructive pattern just by looking at the quesition (if it doesn't tell you to find minima or maxima).


    Thank you
     
  2. jcsd
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