👉 A penumbra is a region of light that appears to be surrounded by a shadow. It is often used in architectural terms, particularly for buildings or structures that are not directly visible from the outside. In mathematics and physics, it refers to the part of an object's surface that is illuminated by a ray of light. For example, consider a cube with sides of length 1 meter. If you shine a beam of light through the center of the cube, the resulting shadow would be a pen
