A double-slit interference experiment shows fringes on a screen. The entire experiment is then immersed in water. Do the fringes on the screen get closer together, farther apart, remain the same, or disappear entirely? Explain.

Get closer together

Explanation:

The refractive index of water is relatively than the refractive index of a vacuum or air. Due to the relationship between speed of light and refractive index, if the refractive index of the medium increases, the speed of light will decrease when the experiment is immersed in water. A reduction in the speed of light will lead to a decrease in wavelength. Mathematically the space between the fringes (Δy) is:

Δy = λ*L/d

Because the variables "L" and "d" are constants, a reduction in wavelength will lead to a reduction in Δy.