Shimmering soap bubbles have a dark side | Science News

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Shimmering soap bubbles have a dark side

Dark spots in soap film grow and merge moments before bubble pops

By
7:00am, January 12, 2017
soap bubble film

HELLO DARKNESS  Just before a soap bubble bursts, its rainbow surface becomes peppered with dark spots in the thinnest regions of the bubble film. Once the darkness spreads over a large area, the bubble pops.

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Zoom in on a soap bubble just before it bursts and brilliant, complex patterns emerge. Shimmery rainbows appear in thicker portions of the soap film, while clusters of dark spots appear in the thinnest regions.

The thickness of the soap film determines the color seen. Light rays that reflect off of the top and bottom of the film combine to amplify particular wavelengths, an effect known as constructive interference. In thicker areas of the film, longer wavelength colors appear, producing a rainbow. Under gravity’s pull, the soap film flows, causing the patterns to shift over time until finally the bubble pops.

When the film becomes even thinner than the shortest wavelength of visible light, dark spots appear, due to destructive interference that cancels out light reflecting off the bubble’s surface. Over about a minute, those spots grow and merge,

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