An oil film whose thickness is 300 nm and whose index of refraction is 1.20 floats on a puddle of water (n = 1.30). For what wavelength (in air) of visible light (between 400 and 800 nm) will there be destructive interference when the film is looked at from above? a) 600 nm amt= A b) 480 nm 400 nm 1 = 2. 300 * 10 9 x 1.3 Dee 720 nm 750 nm