Question

In Young's double slit experiment the separation between the slits is halved and the distance between the slits and screen is doubled . The fringe width is:

• A. Unchanged
• B. Halved
• C. Doubled
• D. Quadrupled

Answer 1

Answer: (D)

Quadrupled

Fringe width $\delta =\frac{\lambda D}{d}$

$\frac{{\delta }_2}{{\delta }_1}=\frac{\frac{\lambda D_2}{d_2}}{\frac{\lambda D_1}{d_1}}$
$=\frac{D_2{d}_1}{D_1{d}_2}=4$