This document discusses how light travels and interacts with matter. It explains that light travels from the sun to earth at a distance of 90 million miles. Light is made up of electric and magnetic waves, and travels faster in a vacuum than in other materials. The document defines transparent, translucent, and opaque materials and how they interact with light. It describes the formation of shadows and the law of reflection. Refraction of light is explained when light passes from one medium to another. The document also discusses the visible spectrum and how different colors of light have different wavelengths.