Light interference – Iridescent colours

Just as with the window, the incident light falling on the soap film is both reflected and transmitted. In contrast, however, a soap film is only a few thousandths of a millimetre thick, and thus only a little bit greater than the wavelength of the visible light.

If the soap film changes its form by being blown, our viewing angle changes, too. There thus appears to be a dependence of the iridescent colours upon the thickness of the soap film, the viewing angle and the wavelength of the light.