What happens if the path difference is not a multiple of lambda?

[pakontam]

take it as em waves.
if the path difference is nlambda, where n is an integer, the interference will be a constructive one.
if the difference is (n+1/2)lambda, it'll be distructive.

what's it if the difference is neither nlambda nor (n+1/2)lambda?

thanks.

 

[dipstik]

then it changes the magnitude of the wave by addition of the two waves of different phase:

E(total)=E(wave1)+E(wave2)
E(wave1)=E*cos(wt)
E(wave2)=E*cos(wt+phi)
where phi=2*Pi*(path_difference/lambda).