Physics - Wave Optics Question with Solution | TestHub

For first dark fringe on either side$\mathrm{dsin}\mathrm{\theta }=\mathrm{\lambda }\mathrm{ }\mathrm{or} \frac{\mathrm{dy}}{\mathrm{D}}=\mathrm{\lambda }$

$\therefore \mathrm{ }\mathrm{y}=\frac{\mathrm{\lambda D}}{\mathrm{d}}$

Therefore distance between two dark fringes on either side$=2\mathrm{y}=\frac{2\mathrm{\lambda D}}{\mathrm{d}}$

Substituting that values, we have

Distance$=\frac{2\left(600\times {10}^{-6} \mathrm{mm}\right)\left(2\times {10}^3 \mathrm{mm}\right)}{\left(1.0\mathrm{ }\mathrm{mm}\right)}=2.4\mathrm{ }\mathrm{mm}$