Light is a form of energy. Light helps us to see object .But it is not visible to us. We can define light as the form of energy which causes in us the sensation of sight. Light always travels from one point to another in straight lines. The light rays travel from one point to another in the form of waves. Light is an electromagnetic wave in nature as it requires a material medium for its propagation .As we have discussed that Light is an electromagnetic wave so its propagation from one point to another depends on the nature of medium through which it passes. That is why the speed of light is very high being 3 × 10-8 meters per second but the speed of light is less in water and glass as compared to speed in vacuum (or air ).
A light wave which travels from one point to another in a straight line path joining them is called a ray of light while a bundle of such rays is called a beam of light.
Sources of Light
These can be divided into two types:
1. Natural sources
2. Artificial sources
Natural Source of Light
The natural source of light occurs naturally. For example Sun, stars, fire fly (jugnu) and radium.
Artificial Source of Light
These are those sources of light which are made by man. That is why these are also called as man made sources. The common examples of artificial sources of light are candles, electric bulb, electric tube, lamp and some chemical reactions.
Test Your Understanding and Answer These Questions:
- What is light?
- What is speed of light in vacuum?
- What are the sources of light?
- Give any three examples of natural sources of light.
- Give any three examples of manmade sources of light.
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