1) A thin layer (231nm) of oil (n=1.41) floats on top of water (n=1.33). What is the largest wavelength of light (in air) that will destructively interfere? What color will the surface appear?
2) 580nm light illuminates a 1500 line-per-cm diffraction grating and produces its 1st order maximum 1cm above the central maximum on a screen, which is a distance L away from the grating. What is L?