A Young double slit experimental setup is immersed in water of refractive index 1 . 33   . It has slit…

The fringe width when Young's double slit experiment setup
is immersed in water,

$y=\frac{\lambda D}{\mu d}$

Substitute the given values in the above equation.

$y=\frac{6300\times {10}^{-10}\times 1.33}{1.33\times {10}^{-3}}$

$y=6.3\times {10}^{-4} \mathrm{m}$

$y=0.63 \mathrm{mm}$