Interference by thin films

Have you ever looked at a spot in a parking lot where oil dripping from a leaky car has created a shallow puddle?

This image of an oil slick is Copyright 2005 Jeff Wignall, and is reproduced from an Instructor Insights column on

Have you ever noticed the intense colors of a butterfly's wing?

Image by Dystopian Optimist licensed under Creative Commons .

These are examples of iridescence, the color produced when sunlight strikes a very thin film of material.