In Young double slit experiment if the maximum intensity of light is Imax then the intensity at path difference λ2 will be)
ϕ=2πλx;x=λ2 ϕ=2πλ×λ2=π=180∘ I=4I0 cos2(ϕ2)=4I0 cos2[90] I=0 [∵ cos90=0]