In an experiment to demonstrate interference of flight using Young's slits, separation of two slits is doubled. In order to maintain same spacing of fringes, distance D of screen from slits must be changed to
Answer & explanation
Correct answer: option 3
$β=\frac{λD}{d}=\frac{λ(2d)}{2d}=β$
i.e., D' = 2D.