1. The problem statement, all variables and given/known data 2. Relevant equations destructive interference occurs at 0.5(lambda), (3/2)(lambda),... 3. The attempt at a solution I found the path difference to be: d=sqrt(4+x^2)-x and this has to be equal to (n)(lambda)/2 where n is an odd integer for destructive interference this does not work out algebraically for me...as the x^2-x^2=0 is this path difference not correct? do I just use f(n)=(nv)/(2d) to find d?