1. Light and sources of light

When we enter a completely dark room, we cannot see anything around us, but everything is visible at the moment we switch on the light. This is because light can be detected with the help of the human eye. Light is a form of energy that helps us to see things around us. Without light, we cannot see an object.

  

How does light help to make things visible?

 

When light rays fall on the object, it will get reflected, and when it enters our eye, we can see the object.

 

The objects which can emit light are known as light sources. There are two sources of light.

  

Artificial sources of light:
The source which emits light artificially is termed as an artificial source of light. Some of the artificial sources of light are the flame of a candle, incandescent lamp, neon lamp, Sodium lamp etc. Artificial sources of light can be classified into three categories they are

When certain objects are treated with a high temperature, they begin to emit light.

  

Luminescent sources:

Certain materials can produce light by accelerating the charges in them. One common way of doing this is bypassing current through the conducting material.

  

Gas Discharge Sources:

When we pass electricity through certain gases at very low pressure, light can be produced.