shadowgraph

A shadowgraph is a visual technique used to observe variations in fluid flow or other transparent substances by detecting differences in how they bend or distort light. When light passes through a medium with varying density or temperature, it bends differently at different points. By shining light through the object and capturing the resulting shadow patterns, shadowgraphs reveal details about flow patterns, turbulence, or temperature changes without contact. This method is commonly used in scientific and engineering studies to analyze dynamic phenomena in liquids and gases, providing valuable insights into behaviors that are otherwise invisible.