Question

what you understand by sorce of light

Answer 1

A source of light is something that has light of its own and gives of the light

Answer 2

Light sources are the different kinds of lamps, bulbs, or other devices used to create artificial light. The choice of light source is very important, both for visual comfort and for energy efficiency.
The sun is the most important source of light. The stars and moon are also natural forms of light. Artificial light is light made by humans, for example candles, fire and oil lamps. The electric light is now the most convenient form of artificial light.