Suppose you illuminate two thin slits by monochromatic coherent light in air and find that they produce their first interference minima at ± 35.05 ∘ on either side of the central bright spot. You then immerse these slits in a transparent liquid and illuminate them with the same light. Now you find that the first minima occur at ± 19.30 ∘ instead. a) What is the index of refraction of this liquid?
Express your answer using four significant figures.