Two very narrow slits are illuminated by monochromatic coherent light in air that has wavelength 560 nm and the interference pattern is observed on a screen that is 4m from the slits. The first interference minima ae located at +/- 58 degrees on either side of the central bright band. You then immerse the slits and the space between the slits and the screen in a transparent liquid and illuminate the slits with the same light. Now the first minima on either side of the central bright band occur at +/- 36 degrees.
What is the distance between the two slits?
What is the refractive index of the liquid?