In a Young’s double slit experiment  d=1 mm,  λ=6000A0 and D=1 m (where d, λ and D have usual meaning). Each of slit individually produces the same intensity on the screen. Then select the correct option(s).

β=Dλd=1×6000×10-1010-3=0.6 mmPhase difference between centre and any point is  ϕThen  Iϕ=4I0cos2ϕ2 ⇒344I0=4I0cos2ϕ2cosϕ2=±32 ⇒ϕ2=π6⇒ϕ=π3 ∴ minimum distance between such points  =2y=2DΔxd=2DΔϕλd2π=21π36000×10-1010-32π=0.2mm