Diffraction versus Refraction

Diffraction versus Refraction

The phenomena of diffraction and refraction are both wave properties. Both these phenomena sound similar because both of them represent some sort of bending of waves. Therefore, these two concepts might appear to be a little confusing to students. This article will highlight the difference between these two phenomena in detail which should be beneficial for students who are fairly new to the subject.



In this phenomenon, waves bend around tiny obstacles and spread out at tiny openings in entering into a region that should have been shadowed. Such a deviation from the initial straight line path is known as diffraction.

The diffraction of waves results in the formation of dark and bright fringe pattern known as “diffraction pattern”. The effects of diffraction can also be observed when light waves travel through media having different refractive indices. Similar effects can also be seen when sound waves travel through media having different acoustic impedances.

The effects are more prominent when the dimensions of the obstacle agree with the wavelength of the wave. When light waves get diffracted by a single slit, a diffraction pattern with darn and bright fringes is observed. The central bright fringe has maximum width and intensity. The intensity of the fringes decreases as we go along either side of the central maxima.


When a wave travels from one medium to another at a specific angle other than 90° and 0°, the line of travel of the wave changes at the interface because of a change in wave velocity. That phenomenon is called refraction. Mostly, light waves are associated with refraction but other waves can also exhibit the phenomenon of refraction.

For example, sound waves exhibit the phenomenon of refraction when they cross 2 media. Water waves also refract depending on the depth of the body. The phenomenon of refraction is accompanied by a change in speed and the wavelength decided by the refractive index of the media.

Refraction of light waves is a commonly observed phenomenon. Most of the strange optical illusions in nature are a good example of refraction.


Both diffraction and refraction are dependent on wavelength. Therefore, both the phenomena can split white light into component wavelengths. But there sore a few noticeable differences. Some of them are:

Diffraction is the spreading or bending of waves around an obstacle. Refraction, on the other hand is the bending of waves due to the change in speed.

Diffraction of light waves result in the production of fringe pattern. Refraction of light, on the other hand creates optical illusions but not fringe patterns.

Another important characteristic of refraction is that it can make objects appear closer than they actually are. Diffraction, on the other hand cannot do that.

In simpler words we can say, refraction is the bending of a wave when it meets an interface between media of 2 different optical densities. This phenomenon happens mainly due to the difference in speeds in media. Diffraction is basically the spreading of a wave that can occur even when the wave propagates in the same medium.

We’ll bring this article to a close for now then. Hope you had a good read.

Sudipto Das

Sudipto writes technical and educational content periodically for wizert.com and backs it up with extensive research and relevant examples. He's an avid reader and a tech enthusiast at the same time with a little bit of “Arsenal Football Club” thrown in as well. He's got a B.Tech in Electronics and Instrumentation.
Follow him on twitter @SudiptoDas1993

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