Reflection of light: When a ray of light falls on a smooth and polished surface, light returns in the same medium. It is called reflection. Shadow: Opaque objects do not allow light to pass through them and cast dark patches behind them. These dark patches are called shadows. Light, Shadows and Reflections will help you in understanding concepts such as opacity, the meaning of shadows, pinhole camera and its construction. This chapter also includes topics of mirrors and reflections, which is very important to understand thoroughly.