Diffraction Definition

The phenomenon in which light bends around the apertures or the corner of the particles spreading into different regions of the geometrical shadow of the aperture is called Diffraction. Diffraction of Light results is due to the superposition of secondary waves from different parts of the same wavefront. For Diffraction to happen the size of the particle or slite must be comparable to the wavelength of the light i.e. d ≈ λ. 

The phenomena of Diffraction can be best observed by Single Slit Experiment. When light passes through a single slit of aperture compared to the wavelength of light then it is expected that screen behind the slit will appear bright and this will be of the size of the aperture of the slit. However, this is not the case, and a larger portion of the screen, greater than the size of the aperture of the slit appears bright. There is a bright spot in the center which is called Central Maxima and on both sides of Central Maxima, there is an alternate bright and dark pattern with decreasing order of intensity.

We generally don’t encounter diffraction in our daily life as the wavelength of light is much smaller than the size of the particles around us. Thus in real life, the interaction of light and larger particles result in shadow which doesn’t happen in the case of diffraction. X-Ray Diffraction helps to determine the particle size of the crystal using Bragg’s Law.

Let’s see some features of diffraction.

Features of Diffraction

There are the following features of Diffraction

• Diffraction happens when light pass through slits or bends around corners of an obstacle
• The size of the aperture of the slit or obstacle must be comparable to the wavelength of light.
• Diffraction from a slit results in a central bright spot
• The diffraction results in unequal fringe width.
• The intensity of the fringes is variable.

Now let’s understand what is interference and what are its features.

Diffraction and Interference are two important phenomena studied in Wave Optics. These phenomena are linked to the Wave Nature of the matter. We know that when photons are emitted from the source they start oscillating in space and the locus of all such oscillating particles in the same phase is called Wavefronts. As per Huygens Wave Theory, each point on the Wavefront acts as a source of secondary Wavelets which later add up to give a new Wavefront. The sources of these Wavefronts can be coherent or non-coherent depending upon whether the phase difference is constant or not. These wavefronts interact with each other and with other particles to give rise to the phenomena of  Interference and Diffraction respectively. 

In this article, we will learn about what is diffraction, what is interference and what are the differences between Diffraction and Interference.