When we look at a leaf we know that it is green in colour because light bounces off the leaf to our eyes to tell us that it is green. But what is light? Which are the sources of light from which light is originated? Light is an electromagnetic radiation. A particular frequency of this radiation (around 390-700 nm) is visible to the human eye. Everything that we see around us is because of light. Light is a form of energy and like all energies, it is produced from a source. In physics, these are called Light sources.
There are countless sources of light but they can all be categorized under either of the two following categories-
The universe is filled with objects that emit light. Some of the light from these sources reach the earth. The following things in nature have the ability to emit light:
Apart from the natural sources, light can be produced artificially too. The different light sources produced artificially can be put under three broad categories-
When certain objects are heated to a high temperature, they begin to emit light. Both infrared and visible light is produced in the process.
Example- Candle, incandescent lamp.
Light can be produced by accelerating charges in a luminescent material. One common way of doing it is by passing current through the material.
Example- Fluorescent tube light, electric bulb
Passing electricity through certain gases at a very low pressure can produce light too.
Example – Neon lamp, Sodium lamp.