We will learn in this session how does light interact with matters. We will illustrate a couple of examples for better understanding. Let’s explore.
Like other substances, Light also interacts with matters. To understand, we will take one mirror, one football, and one glass. Now, if we bring all the objects under light, we will see, each object will interact with light differently. If we take another few objects also, there will be three scenarios:
Look at the diagram,
Reflection means bouncing off the light from an object. We have seen reflection happened in the mirror because the surface of the mirror is very smooth and shiny. The smooth and shiny surface can be:
There are a few rules of reflection, which we will study later.
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Absorption of light means if the light falls on an object, the object will absorb the light. We have seen absorption in football. Absorption of the light can happen on so many objects:
Transmission means when light passes through the object. We have seen transmission in the glasses. The object can be:
There are a few differences between Reflection Absorption & Transmission. These are:
| Reflection | Absorption | Transmission |
| When Light rays fall on an object, it will bounce off | When Light rays fall on an object, it will be absorbed | When Light rays fall on an object, it will be passed through the object |
| Reflection happens on a shiny surface | Absorption happens on any surface other than very shiny surfaces | Transmission happens on transparent type surfaces |
| Example: Mirrors, Plain water surface, etc. | Example: Brick, book, etc. | Example: Glass, water, air, etc. |
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The mirror is made of glass, hence, it is very simple to conclude that transmission will happen. Why do we use a mirror? To see ourselves, basically, we see our images and comb our hair! However, if transmission happens in the mirror then we should not have seen our images.
Then how is it possible? If we observe carefully, we will see that there is a coating of silver nitrate in the back of the mirror and due to that coating, light rays can not pass through the glass of the mirror & bounces back to our eyes and we see ourselves.
Hence, though it is glass, due to coating, light rays will be reflected. There may be very little absorption but since the surface is very shiny, absorption is negligible.
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