If the oil thickness is 200 nm and the index is 1.5, what (vacuum) wavelength (in nm) does a diver see looking at the same position as the scientist, but from under water?

Two solutions of the same uv-absorbing molecule were analyzed by uv-vis spectroscopy on the same instrument using 1 cm pathlength cells. use data from the table to calculate by what percentage the concentration of solution b is compared to that of solution a.sample absorbance at 315nm a 0.45 b 0.80