2008 HS Photo Contest Pictures

2008 AAPT High School Physics Photo Contest
Winner's Showcase

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Third Place - Contrived

Title: Cross-Polarization
Student: Carly Sobecki
School: Convent of the Sacred Heart, Greenwich, CT
Teacher: Mr. John Paul Reid

This photo demonstrates cross-polarization of light. To contrive this effect, the objects were placed between two polarizing filters, one over the camera’s lens and one above the light source. The two filters polarized in perpendicular directions. Since the light is only oscillating in one plane after traveling through the first filter, all light is blocked from reaching the lens by the second filter which only allows light traveling in the perpendicular plane. For this reason, the bright background appears black. When the polarized light contacts the plastic silverware, it is randomized and loses a degree of polarization. Consequently, some of this light is traveling in the perpendicular plane and is able to pass through the second polarizing filter. The plastic, which has a different optical density than air, diffracts the light as it passes through due to thin-film interference. Since the angle of diffraction depends on the wave’s frequency, and each color of light transmits at a discrete frequency, the originally white light is separated and each color is visibly distinct. These phenomena together produce the brilliant display observed in the photograph.