In young's double slit experiment, the separation between slits is trippled and distance between the slits is made one third. The fringe width is
Answer & explanation
Correct answer: option 4
$β=\frac{λD}{d}$
$∵β'=\frac{λ(D/3)}{3d}=\frac{λD}{d}.\frac{1}{9}$
Thus, the fringe width becomes one ninth.