Why does oil interfere and water doesn't? (Rainy ground)

because the oil layer is very thin, the distance between the upper and lower surfaces is an order of magnitude with the wavelength of light, the reflected light from the upper and lower surfaces can interfere, and the water layer is very thick. Therefore, although the emitted light from the upper and lower surfaces can interfere, the phenomenon is not obvious. In fact, if the water layer is as thin as the oil layer, obvious interference can occur, resulting in a colorful film. The rainbow is the dispersion phenomenon of sunlight in the air because of small water droplets, which has nothing to do with interference.