The swirling psychedelic colors of a soap bubble come from the interference of light rays bouncing off the inner and outer surfaces of the film. As a result, the colors we see are directly related to the thickness of the soap film. Over time, as a film drains, black spots will appear in it. This happens where the bubble’s wall becomes thinner than the wavelength of visible light. Black spots will grow and merge as the film continues to thin. Then, when it’s too thin to hold together any longer, the bubble will pop and disappear. (Image credit: L. Shen et al., source)
Soapy Rainbows
