The Hidden Rainbows in My Phone Case
Mingrui Cao
Award: Top 100
School: beijing national day school
Teacher: long li
Category: Contrived
Photo #19318
The Hidden Rainbows in My Phone Case
I love messing around with my photography gear. One day, I placed my clear phone case between two circular polarizers (CPL) and saw with astonishment how rainbow-colored patterns appeared onto the case.
Very much enthralled by this beautiful phenomenon, I did some digging. I learned that this happens because the plastic is birefringent--a fancy word meaning it bends light in two different ways (o-ray and e-ray) due to its anisotropic, or direction-dependent, refractive properties. When polarized light passes through, the phone case splits it into two beams, making them out of phase with each other. As the two polarized light waves recombine after passing through the birefringent material, their phase difference causes constructive interference for some wavelengths and destructive interference for others.
Even more exciting, this is not only a cool party trick--it's actually extremely practical. Structural engineers use this effect to check for stress points in transparent materials, which might be created during the manufacturing process, such as molding and casting. I captured a moment where ordinary objects turn into something quite remarkable, which is truly delightful.
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