The Diffraction of Light: A Basic Overview

The Diffraction of Light: A Basic Overview

Diffraction refers to those phenomena that occur when a wave encounters a slit or an obstacle.

It’s defined to be the bending of light around the corners of an aperture or an obstacle. These effects also occur when light travels through a medium having varying refractive index or when sound waves travel through a medium having varying acoustic impedance.

Diffraction is not limited to only sound or light waves. It occurs with all waves including the likes of sound, water, electromagnetic waves (visible light, radio waves and X-rays). We’ll discuss this matter in greater detail in this article.

The amount of bending is dependent on the relative size of the wavelength of light to the size of the slit (opening). If the slit is noticeably larger than the wavelength of light, the bending of the light will be almost unnoticeable. If the slit and the wavelength of light are almost equal in size, the amount of bending can be noticed easily with the naked eye.



Diffraction arises due to the way through which waves propagate. The propagation of waves can be envisioned by considering each and every particle of transmitted medium on a wave-front.

A qualitative understanding of diffraction phenomenon can be obtained by considering the way through which the relative phases of individual secondary wave sources vary; more specifically, the conditions in which the phase difference is equal to half a cycle.

The basic descriptions of diffraction are practically those in which the situation is reduced to a 2-dimensional problem.

Diffracted light in the Atmosphere

In the atmosphere, light actually gets diffracted around atmospheric particles. These atmospheric particles are minute water droplets found in clouds. Fringes of dark, light or colored bands are produced from diffracted light.

A simple example of this is the silver lining found at the edges of clouds. The coronas that surround the sun or the moon can also be considered a good example of this phenomenon. The illustrative image shown above depicts the way through which light bends around tiny cloud droplets.

 Optical effects from diffraction              

The interference of light waves results in the production of optical effects. The optical effects of diffraction are often visualized in everyday life. A simple example can be a CD or a DVD. The closely spaced tracks on a DVD or a CD act as a diffraction grating thereby forming similar rainbow patterns. You have surely seen that a lot if you handle a lot of CDs/DVDs. Just keep an eye out for the next time when you handle DVDs/CDs and you’ll surely understand what we are talking about.


Diffraction grating on a compact disk

There are several other optical effects of diffraction. If you are enthusiastic enough, you can always browse the internet for more information on the subject and of course, you will have to keep your eyes open at the same time to detect those effects from your daily life activities. After all, seeing is believing.

We’ll sign off for now. Hope you had a good read.

Sudipto Das

Sudipto writes technical and educational content periodically for 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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