What is the Difference between Interference and Diffraction?

Interference and diffraction are important concepts in physics. In this article, we will be explaining these two concepts and the difference between the two as well.

Table of Contents

• Difference between Interference and Diffraction
• What is Interference?
• What is Diffraction?
• Similarities between Interference and Diffraction

Difference between Interference and Diffraction

Interference and diffraction are two important phenomena in Physics. The following table shows the difference between interference and diffraction:

Parameter	Interference	Diffraction
Cause	Interference happens when two light waves meet and mix together. It is caused by two or more light waves coming together.	Diffraction happens when a light wave bends around corners or through small openings. It is caused by light waves hitting an obstacle or passing through a small gap.
Sources of Light	Needs light from sources that stay in step with each other.	Can happen with light from just one source.
Patterns Formed	Makes patterns of bright and dark bands.	Makes a pattern with a central bright spot and other spots that get dimmer further out.
Requirements	The path difference between waves should be a multiple of the wavelength.	The size of the gap or obstacle should be close to the light's wavelength.
Uses	Used in things like holograms and measuring tiny distances.	Used in tools for splitting light into a spectrum, like in CDs or DVDs.
Famous Experiments	Young's double-slit experiment shows this.	Single-slit experiments show how light spreads out.
Relation to Wavelength	The spacing in the pattern depends on the light's wavelength and the setup.	The size of the spread-out light pattern depends on the wavelength.

What is Interference?

Interference is a type of phenomenon which occurs when two or more waves overlap and combine together. It can happen with any kind of wave such as sound or water waves. Imagine you have two sets of waves, maybe from two different stones thrown into a pond. When these waves meet, they don't just pass through each other. Instead, they interact and combine in interesting ways. There are two types of interference including constructive and destructive. 

Constructive interference happens when the peaks (high points) of two waves line up together. This makes a new wave that's bigger than either of the original waves. Destructive interference is the opposite. It happens when a peak of one wave lines up with a trough (low point) of another wave. When this happens, the waves cancel each other out, making a smaller wave or even no wave at all.

In light waves, this interference creates patterns of light and dark. A good example of this is when you see colourful patterns in a soap bubble. Besides soap bubbles, you can see interference in other places. For example, when you look at a CD or DVD, the colorful patterns you see are due to light waves interfering. In science, interference is used in tools like microscopes and in techniques like holography to create 3D images.

What is Diffraction?

Diffraction is a phenomenon associated with waves, such as light, sound, or water waves. It occurs when a wave encounters any obstacle or slit comparable in size to its wavelength. Diffraction also happens when waves pass through a small opening or gap. The waves spread out after they pass through the gap. It is a common phenomenon and can happen with any type of wave. Light waves diffract too, but it's more noticeable when the size of the obstacle or opening is close to the wavelength of the light. 

When light diffracts through a small slit or opening, it creates a pattern of light and dark bands, known as a diffraction pattern. These patterns can tell scientists a lot about the light, like its wavelength. A good example is when you see a beam of sunlight coming through a small opening in curtains and the light spreads out into the room. One way you might have seen diffraction is through the spreading of colors in a CD or DVD. The tracks on the disc diffract the light, splitting it into different colours.

Similarities between Interference and Diffraction

Interference and diffraction are both about how light waves behave, and they have some things in common. Here is how they are similar, explained in a simple way:

1. Both Are About Waves: Interference and diffraction happen with waves, like light or sound waves. They show us how waves can bend, spread out, or overlap.
2. Superposition Principle: When two waves meet, the new wave they create is just the sum of the two original waves. This idea is key in both interference and diffraction.
3. Spatial Patterns: Both interference and diffraction result in spatial patterns (like fringes or bands of light and dark areas). These can be observed and measured. Such patterns are used in various applications in science and technology.
4. Dependent on Wavelength: The patterns we see in both interference and diffraction depend a lot on the wavelength, or colour, of the light.