Question

What would happen to the distance between the bright fringes produced by a diffraction grating if the entire interference apparatus (light source, grating, and screen) were immersed in water

Answer 1

Answer:

Since the wavelength would be reduced by the factor of N where N is the index of refraction, fringes would be be closer to one another.

(Similar to the difference of fringes of red light and blue light.)