22. In Young’s double slit experiment, if the separation between coherent sources is halved and the distance of the screen from the coherent sources is doubled, then the fringe width becomes :

22. In Young’s double slit experiment, if the separation between coherent sources is halved and the distance of the screen from the coherent sources is doubled, then the fringe width becomes :

(a) half

(b) one-fourth

(c) four times

(d) double

Answer :  (c) four times

\( \beta = \dfrac{\lambda D}{d} \)

\( \beta_{2} = \dfrac{\lambda \, 2D}{d/2} \)

\( = \dfrac{\lambda D}{d} \cdot 4 \)