The different light sources produced artificially can be put under three broad category

1. Incandescent source
2. Luminescent source
3. Gas discharge source

1. Incandescent source

When certain object are heated to a high temperature , they being to emit light. Both infrared and visible light is produced in the process.

Example - candle , incandescent lamp.

2. Luminescent source

Light can be produced by accelerating charge in a luminescent material. One common way of doing it is by passing current through a material.

Example- electric bulb

3. Gas discharge source

Passing electricity through a certain gases at a very low pressure produce light too.

Example- neon lamp, sodium lamp.