$6.$ A predatory Angler Fish has evolved bioluminescence, so that it can make its own light that it uses like a flashlight to help see its prey. A species of jellyfish lives in deep ocean water $($so that the only light that reaches it is the light produced by the angler fish$).$ The body of the jellyfish is mostly water surrounded by a $$thin film$$ of transparent cells with an index of refraction $=1\mathrm{.}50.$ If the body of the jellyfish is $.$ thick, what color of light should the fish produce to be able to see the jellyfish? $($Two colors will work. Tell me either one.$)$