Arizona Memorial & Oil Spillage

The Junior Pearl Harbor visit this Friday proved not only beneficial for our APUSH class, but also provided great review materials for AP Physics. Even the introductory movie was action-packed with references to physics principles such as momentum, buoyant  force, kinetic energy, air resistance, torpedo launchers, engines, and electricity, just to name a few. However, the most exciting part of the trip was at the actual memorial, where in the water, there still exists the remnants of the tons of oil that kept the harbor burning for two days after the Japanese attack. There, my fellow classmates and I took the time to scatter a few flowers in honor of those who died in the bombing, and we soon noticed the layer rainbow on the water caused by the oil. I solemnly reflected on the principles behind the circle of colors, thin-film interference. I concluded that the rainbow color was due to the differing thickness of the sheet of oil at different spots. White light would hit the oil film and be refracted with a phase change of 180 degrees (the index of refraction increases from air to oil) and reflected, the refracted ray is again reflected and refracted on the surface between water and oil. The second time there is no phase change (the index decreases from oil to water). Thus when the two reflected rays interfere on the on the other side of the oil, they either end up completely in phase, completely out of phase, or somewhere in between depending on the path difference of the rays, which equals about twice the thickness of the film. So when there are different thicknesses to the film, a range of different colors result.

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