Light is a form of energy emitted by bodies under certain conditions. A luminous body is one that emits its own light example- sun. Non luminous bodies are objects that reflect light from luminous bodies. example- moonSources of light can be classified as natural or artificial. Natural sources, such as our Sun and other stars, cannot be controlled by us. Artificial sources, such as electric lamps and candle flames, are controllable.Whether a body is luminous or non-luminous depends not only on the material of the body but also on its condition. The tungsten filament of an electric light globe is non-luminous until an electric current is passed through it. When a piece of iron or nichrome wire is heated strongly enough it becomes white hot. Materials that emit light when heated are said to be incandescent.