Soap bubble film iridescence. Light micrograph of the surface of a bubble of soap showing light interference effects. The swirling pattern of colour occurs by light reflection through the thin film of soap. The thickness of the soap film varies across the bubble, affecting the wavelength of incident white light. Certain wavelengths of white light are extinguished, producing a colour interference pattern as seen here. The oily surface of the soap bubble contributes to the swirling effect of the colours. Magnification: x13 at 35mm size.