Light, Force, and Color
DIANKUN GAO
Award: Top 100
School: the experimental high school attached to beijing normal university
Teacher: he dao
Category: Contrived
Photo #21552
Light, Force, and Color
"This image is a photoelastic photograph of a bent plastic case using a white light source and two orthogonally aligned polarizing filters, which I took while conducting an experiment at the optical lab using my Canon R5 with RF24-105 F4 L IS USM. The image reveals how mechanical stress is distributed through the acrylic part of the case.
In this experiment, an external bending force was applied to the center of a plastic case containing both acrylic and transparent sections, and the sample was placed between two crossed polarizers. Under stress, the acrylic loses its optical isotropy and becomes optically anisotropic, a phenomenon known as the photoelastic effect. As polarized light passes through the stressed material, different regions rotate the light by different amounts depending on the local stress, producing vivid colored fringes.
The colorful regions correspond to the acrylic area, where the stress pattern becomes visible, while the black square in the center corresponds to the transparent section where light passes directly through the plastic, showing the completely darkness caused by the polarizers. The denser color lumps near edges and corners indicate stronger stress concentrations.
I also used a multiple-exposure technique and rotated the plastic by 90 degrees without changing its shape or the applied force, creating a symmetrical clover-like pattern. In this way, the photograph makes otherwise invisible mechanical information visible through color and light."
|
