Answer:
![0.75\ cm](https://img.qammunity.org/2022/formulas/physics/high-school/xql9xul54h3rvgqiwi0l88c95vr02gcxpo.png)
Step-by-step explanation:
Given
Wavelength of light
![\lambda=500\ nm](https://img.qammunity.org/2022/formulas/physics/high-school/y6a50s025x3ljlemkrt9qthjudn2w65cbz.png)
Screen is
away
Distance between two adjacent bright fringe is
![\Delta y=(\lambda D)/(d)](https://img.qammunity.org/2022/formulas/physics/high-school/3erhezv78mxkifohvleomu0dm11zkby5tu.png)
When same experiment done in water, wavelength reduce to
![(\lambda )/(\mu)](https://img.qammunity.org/2022/formulas/physics/high-school/d9hylzmdw2yqp81qectgfltg0ffcr9rnxx.png)
So, the distance between the two adjacent bright fringe is
![\Delta y'=(\lambda D)/(\mu d)](https://img.qammunity.org/2022/formulas/physics/high-school/ogtopagfcw16uw2952ff3ilg6abt7yhjar.png)
Keeping other factor same, distance becomes
![\Rightarrow (1)/((4)/(3))=(3)/(4)\quad \text{Refractive index of water is }(4)/(3)\\\\\Rightarrow 0.75\ cm](https://img.qammunity.org/2022/formulas/physics/high-school/dege0vouhs2hhy5h64l8lmse93pstwovnu.png)