caption: The image shows a white background with a hexagonal prism in the center, surrounded by lines and text written on it. The prism is a tetrahedron, which is a type of polyhedron that is composed of two sides connected by a central point and two sides on either side. The sides of the prism are connected by arrows, indicating the direction of the light passing through them. The text on the prism is written in a bold font and is likely a description of the structure.