After heavy rain, an engine oil was accidentally dropped on a wet concrete road. People observed that the color of the oil floating on water appear to be bright red when viewed almost perpendicularly on the surface, see Figure 3.4. If light falls perpendicularly on the thin oil film and the wavelength of red light in vacuum is Avacuum = 650 nm, calculate the nonzero minimum thickness t of the film.

After heavy rain, an engine oil was accidentally dropped on a wet concrete road. People observed that the color of the oil floating on water appear to be bright red when viewed almost perpendicularly on the surface, see Figure 3.4. If light falls perpendicularly on the thin oil film and the wavelength of red light in vacuum is Avacuum = 650 nm, calculate the nonzero minimum thickness t of the film.