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Samiksha Gupta

Updated on 07th June, 2023 , 6 min read

What is the Difference Between Interference and Diffraction?

Difference Between Interference and Diffraction Overview

The law of diffraction is very useful in the production and design of contemporary technical devices or instruments that can assist researchers in identifying the properties of a specific substance. Our natural environment contains crystals, and the molecular makeup of those crystals can vary. The atomic locations of some basic crystals cause them to diffract X-rays because their planes of atoms are evenly spaced. Bragg's law has demonstrated it.

Based on the idea of diffraction, scientists have created a specific type of equipment known as a diffractometer. This specific equipment uses X-ray diffraction to create diffraction patterns, which are then compared between various crystal types to identify and ascertain the various molecular structures of various crystal types.

The idea of interference is frequently applied in many optical testing methods. The surface quality is specifically tested using this idea. This concept also has several real-world applications, which can be highlighted. When obtaining photos from equipment like telescopes and calculating light intensity, the idea of interference is applied. When light travels through a small space, such as a lane, it spreads out into the shadows and causes interference between the resulting waves. What then is interference? When two or more electromagnetic waveforms combine to create a new wave, the displacement is either strengthened or cancelled, creating interference.

Key Difference Between Interference and Diffraction

Examining the region of the least intensity, which is extremely dark in interference and less dark in diffraction, is crucial to understanding their main distinctions. There are a few other things that set diffraction apart from interference in addition to these few distinctions. Understanding the differences between the two is crucial. The following is a list of some essential differences between diffraction and interference:

Parameters

Diffraction

Interference

Definition

Diffraction is referred to as secondary waves that split off from the original wave.

Waves from two independent sources that produce different wavefronts are said to be causing interference.

Occurrence

The secondary wavelengths' superposition is what causes it to happen.

It happens as a result of the superposition of light waves from two sources.

Contrast

The contrast between minima and maxima is very poor.

The contrast between minima and maxima is very good.

Width of fringes

The width of the wavelength is unequal.

The width of the wavelength is equal.

The intensity of fringe

For all fringes, diffraction causes differences.

The fringes all have the same intensity

Obstacle or slit

Required

Not required

Fringe spacing

It is non-uniform.

It is uniform.

Wave propagation direction

It changes after diffraction

It does not change after interference. 

What is Diffraction? 

When light travels through a slit or other small opening, the process known as diffraction causes the light wave to spread out. However, it is important to note that the slit's size and the wave's wavelength must be comparable in this case.

The light wave won't curve at the corners like it did in the case of the wide opening. While the bending is extremely obvious in smaller openings. However, due to the slit's extremely small size, the opening functions as a separate source and permits the wave to propagate across the entire surface after the slit.

diffraction vs interference

What is Interference?

Superposition of two or more light waves from two coherent sources travelling through the same medium is known as interference. We are aware that coherent sources emit light waves with a constant phase difference and the same frequency.

Therefore, when two coherent waves cross each other, they superimpose one another. The disruptions caused by several waves can therefore be added algebraically as a result of the superposition of the waves. It should be noted that the amplitude and phase relationship between the two component waves determine the intensity of the resulting wave.

diffraction vs interference

Interference can be categorized into two categories:

1. Constructive Interference: The resultant wave's intensity will be higher than the two individual waves when the two superposing waves have the same amplitude and phase. More exactly, the resultant wave will have an amplitude that is twice as large as the waves that will be superposed.

2. Destructive Interference: The intensity of the resultant wave will be lower than the intensity of the two independent waves if the two superposing waves have the same amplitude but opposite phases. The two waves' amplitudes will be summed, but because their phases are opposing, they will cancel one another out.

Difference Between Interference and Diffraction of Light

When two or more waves clash and superimpose to create a new wave, this occurrence is known as interference. Depending on how the peaks and troughs of the overlapping waves are superimposed or aligned, the new wave may have a bigger, smaller, or equal amplitude. Diffraction is the process of light bending around a corner so that it spreads out and illuminates a space. Due to the fact that both diffraction and interference occur at the same time, it is typically challenging to tell them apart. As sunlight passes through or hits a cloud, a silver line forms in the sky. The sun's diffraction is to blame for this.

Interference of Light

Diffraction of Light

Waves interfere as they travel behind barriers.

In the course of diffraction, some places in the space of the wave oscillations are amplified while others are cancelled or modified.

Waves in an interference pattern stay away from the original route in the same elastic environment.

Wave superposition takes place in the same material environment.

The length of cracks and obstructions should be equal.

The waves are referred to as coherent waves since there is a constant phase difference between them. We investigate coherent waves through the diffraction patterns.

After interference, the wave's propagation direction doesn't change.

The propagation direction of waves after diffraction is constant.

An obstacle or slit need not be present for interference to occur.

For interference, a slit or obstacle is required.

The spacing is Uniform.

Non-Uniform Spacing.

Wave superposition in interference starts with shifting wavefronts. It suggests that there is a phase difference between the two waves or that they are not coherent.

In the case of diffraction, the superposition starts with different wavefront segments. It suggests that the sources are coherent or that there is no phase difference between the waves they are emitting.

Difference Between Interference and Diffraction of Wave

While diffraction is brought on by secondary wavelets that originate from the same wave but appear in different regions of it, interference is a feature brought on by waves from two independent coherent sources. By examining the region of least intensity, which is extremely dark in interference but less dark in diffraction, it is crucial to comprehend the underlying differences between them. In addition to these few distinctions, which are listed below, there are a few other factors that set diffraction apart from interference.

Interference of Wave

Diffraction of Wave

Interference is caused when two waveforms coming from two different coherent sources are superimposed or overlapped.

Diffraction is brought on by the superposition of secondary wavelets from various regions of the wavelength.

The fringe width in interference is often constant.

The fringes in diffraction have different sizes.

Additionally, we saw that both dark and light fringes had the same intensity.

The intensity drops off quickly. It denotes that succeeding fringes in a diffraction pattern get less intense.

All maxima in interference have the same intensity level.

The maxima's magnitude can change.

Peaks and minima are well contrasted in interference.

The contrast between peaks and minima is minimal for diffraction.

Also read more about the- .

Difference Between Interference and Diffraction: Things to Remember

  1. Diffraction is the process of light bending around corners such that it spreads out and brightens areas where a shadow is anticipated.
  2. When two or more waves overlap or collide, a new wave is created that may have a higher, smaller, or equal amplitude depending on the type of superimposition or the alignment of the peaks and troughs of the overlapping waves. This phenomena is known as interference.
  3. While diffraction is brought on by secondary wavelets that originate from the same wave but appear in different regions of it, interference is a feature brought on by waves from two independent coherent sources.
  4. All maxima in interference have the same intensity level. While, the maxima's magnitude can change.
  5. Peaks and minima are well contrasted in interference. In contrast, there is little contrast between maxima and minima in the case of diffraction.

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Frequently Asked Questions

Ans. Regarding their occurrence, diffraction and interference have significant differences. Diffraction also happens as a result of the superposition of the secondary wavelengths. In contrast, interference happens as a result of the superposition of light waves from two sources.

Ans. Constructive interference and destructive interference are the two types of interference. Additionally, when the phase and amplitude of the two superposing waves coincide, constructive interference occurs. Destructive interference, on the other hand, occurs when two superposing waves have the same amplitude but are in the opposite phase.

Ans. Following diffraction, the direction of wave propagation changes without a doubt. As opposed to interference, the direction of the wave does not alter following superposition.

Ans. A resultant wave is created when the amplitudes of two waves that are travelling in phase coincide. Constructive interference of waves is what this is called.

Ans. The amplitude of two waves cancels out when they are fully out of phase with one another. Destructive interference of waves is what this is.

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