This is a photo of leaked gasoline after rain. The gas floats above the layer of water, creating two films on the ground. As light strikes the ground, light is either reflected or transmitted after hitting the gas. The transmitted then travelled through the gas, reached the water, and is reflected back out again. Because the two layers have different thickness and density (or more precisely different refractive index), the angle at which the two groups of light reflect were discordant.

As a result, an effective interference was created and our eyes see this beautiful chromatic fade. The strong sunlight helped the colours to pop out nicely.

This photo both proves the phenomenon of “Thin-film Interference” and captures the elegance of physics.

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Davis Jian Kun Zhu
St. George's School, Vancouver, BC
First Prize ( 2015 High School Individual Category )

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