A light-weight and energy-efficient lighting panel is constructed from a light-transmissive and light diffusive extrusion formed to have elongated hollows, which are hollow structures or volumes between two surfaces, at least one of which is transmissive and diffusive. Light projected into the hollow flows through the hollow and part of the light is emitted through the light transmissive and diffusive surfaces. Even though the light sources are located at the edges of a panel, the surface of the panel appears to be uniformly light by light sources distribute directly behind the panels rather than along the edges.