An oil film covers the surface of a small pond. The refractive index of the oil is greater than that of water. At one point, the film has the smallest non-zero thickness for destructive interference in reflected light when infrared radiation of wavelength 800nm is incident normally. When viewed normally at this same point, for which visible wavelengths, if any, will there be constructive interference? Visible light has wavelengths between 400nm and 700nm.