Introduction to Light

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Concept of Light

We have five senses that help us to interact with the world around us: sight, hearing, taste, smell and touch. Out of these, the sense of sight is the most important. We perceive almost 80 per cent of the world around us by using our sense of sight.

We can see the objects around us because of the light coming from these objects. The light from these objects travels in space and reaches our eyes. When it is dark or at night, when there is no light, we are unable to see objects clearly.

Based on the capability of objects to generate light, we can classify them into two types:

• Luminous objects

 The objects that generate their own light are called Luminous objects, which include the sun, fluorescent bulbs, burning candles, etc.

• Non-luminous objects

 Objects that cannot generate their own light are called Non-luminous objects. The table, chair, wall, paper are a few examples of non-luminous objects.

How does Light Help Us See Objects?

We can see non-luminous objects because of the reflection of light. The light of the luminous objects falling on the surfaces of non-luminous objects. These objects then reflect this light, and this reflected light travels towards our eyes and we are able to see them.

 For example, when a torch is lit in a dark room, we are able to see the dust particles in the light. This is because the light from the torch gets reflected from the surfaces of dust particles, which travels towards our eyes and the dust becomes visible.

Also, we are able to see blue skies, the white clouds and the green grass because the light from the sun is getting reflected by them and travelling towards our eyes. During night time, we are able to see the moon because it is reflecting the light from the sun. Note that the moon is non- luminous and it cannot generate its own light.

Summary