Q: In Young’s double slit experiment, the separation between the slits is halved and the distance between the slits and the screen is doubled. The fringe width is
(A) unchanged
(B) halved
(C) doubled
(D) quadrupled
Ans: (d)
Sol: Fringe Width , $\large \beta = \frac{\lambda D}{d}$
$\large \beta’ = \frac{\lambda (2D)}{d/2} = 4 \frac{\lambda D}{d}$
$\large \beta’ = 4 \beta $
Hence , fringe width becomes 4 times .