When Young's double slit experiment is conducted in water,

Step-by-step solution

The fringe width in Young's double slit experiment is given by = D d , where is the wavelength of light, D is the distance between the slits and the screen, and d is the distance between the slits. When the experiment is conducted in water, the wavelength of light changes to ' = , where is the refractive index of water. The new fringe width becomes ' = ' D d = D d = . Since the refractive index of water > 1 , the new fringe width ' is less than the original fringe width . Therefore, the fringe width will decrease.