The beautiful colours that you can see on a soap bubble are the result of the interference of visible light waves off the front and back surfaces of the soap films membrane. The illustration below shows incident light waves striking the film with reflections from the top and bottom surfaces. These reflected light waves interfere with one another to suppress some colours and enhance others. The colours produce depend on the thickness of the film at that point. The thickness of the film changes continually due to laminar and turbulent currents of water gushing around within the lipid bilayer interior, from air currents brushing over the surface and due to shrinkage of the film due to draining.
A Closeup of Soap!
What is it you might ask? This is a close-up of one of our defenses against COVID-19, Soap! Magnified approximately 250 times, the mezmerising colours come about due to thin film interference. The process of thin film interference in soap occurs when light reflects off the top and bottom surfaces of the double-layered lipid film, providing that the film is thin enough. In order for this kind of interference to occur, the thickness of the film must lie in the nanometer regime. Water gushing around inside the bilayer causes the colours to swirl and the patterns to evolve with time. Where the film is extremely thin, it appears as black as the cosmic abyss.
The photography is of particular importance not only as scienceart and science education but also during these frightening times of the COVID-19 Pandemic. The rainbow colours represent the colours of support to primary health care workers.
Thank you to Kevin Kendle for the kind permission to use his music for the background. The song is called "Merope" from his album "Light from the Pleiades".