Ray diagrams represent the path and direction of light using straight lines and arrows. Reflection uses equal angles to the normal; refraction uses the change of direction at a medium boundary. A real image forms where rays meet; a virtual image is located where backward extensions appear to meet. Keep extensions visually distinct from actual light paths. Example: Trace an oblique ray from air into glass. Draw a normal and bend the ray towards it, then add a direction arrow. Justify your answer.