# Diffraction and Its Types

Light is a very important part of our daily life. Without light you cannot see anything. So, it becomes necessary to know about its properties. Diffraction is just one of its properties. In this article you will get to know about Diffraction in a detailed manner.

First of all let us have a look at the following ray diagrams and observe some important things. Have a look at these diagrams and their explanations:

Fig. 1

Okay! Now let’s move on to the explanation part. Light travels in a straight line and produces shadow if an obstacle is placed in its path (as shown in Fig. 1). To be precise, a geometrical shadow is produced in the region A’B’. The light does not enter the shadow region.

Fig. 2

Coming to Fig. 2 we can observe that a slit AB is placed in the path of light. It then produces illumination on the screen in the region A’B’. On the either side of A’B’, there is a geometrical shadow as shown in the figure. The light does not enter in the shadow region.

But! If the size of the slit (Fig.2) or obstacle (Fig.1) is very small and is comparable to the wavelength of light, then light enters in shadow region. Light bends around the edges of the obstacle or slit and enters in the regions of geometrical shadow.

From this we can define diffraction as “The bending of light near the edges of an obstacle or slit and spreading into the region of geometrical shadow is known as diffraction of light”

Not understood? Neither did I when I heard this definition for the first time. So, I thought that this phenomenon is very similar to that of refraction of light. And that’s why I define diffraction as ‘Different type of Refraction’. That is easy to understand only if you know what refraction is, isn’t it?

Examples:

1.       When the sun is seen through a fine piece of cloth, a colored spectrum is observed.

2.       The luminous border that surrounds the profile of a mountain just before sun rises behind it.

In case you did not get the example then just have a look at the following image and you will get an exact idea of what diffraction is.

Isn’t this beautiful? 7 colors playing with themselves and creating magic! This is the real beauty of science, right?

Now we have 2 main types of diffractions. They are:

1.       Fraunhofer Diffraction: The source of light and screen on which diffraction pattern is obtained are at effectively infinite distances from the diffracting system.

2.       Fresnel diffraction: The source of light and screen on which diffraction pattern is obtained are kept at finite distances from the diffracting system.

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