On a Rainy day, Small Oily Films on Water Show Brilliant color. This is due to
When petrol is dropped on the road during a rainy day, a thin layer of oil will appear on the water surface. Both the top and bottom surfaces of this oil film can reflect light. If the path difference between two light rays is an integral times of the wavelength, there will be constructive interference. A light ray will pass through different thickness of oil when the angle of reflection varies.