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Single Slit vs. Double Slit Diffraction: A Comprehensive Comparison

Single Slit vs. Double Slit Diffraction: A Comprehensive Comparison

Light is a unique phenomenon in the natural world. It exhibits all sorts of patterns as it travels through space, from straight lines to curved paths to interference patterns and even diffraction. These different properties can be used to study light and its interactions with matter or be appreciated for their beauty.

Diffraction is the bending of waves around small objects. The diffraction effect can be seen in wave interference, which occurs when two waves overlap and add together. You can study single-slit and double-slit diffractions are phenomena used to study diffraction.

Single-slit and double-slit diffraction are two ways light interacts with a slitted barrier. The main difference between single-slit and double-slit diffraction is that the former is a continuous light pattern while the latter is a discrete pattern.

Moreover, single slits can only create a single line of interference with no width or depth. Double slits can create multiple lines of interference with both width and depth.

Let’s discuss these two procedures in detail.

What Is Diffraction?

Diffraction is the phenomenon that occurs when light passes through a narrow opening or slit. The light waves bend as they pass through the opening, and this causes them to spread out.

Behavioral pattern of light.
A behavioral pattern of bending and spreading light after passing through a slit.

In a beam of light, the different wavelengths (colors) are not all in precisely the same place. They are slightly out of step with one another, known as interference.

When a beam of light passes through an opening in front of it, this interference causes diffraction; some wavelengths are bent more than others.

What Is Single Slit Diffraction?

Single-slit diffraction is a phenomenon that occurs when light passes through a narrow slit and spreads out into a pattern of light and dark areas on a screen. This happens because light waves interfere with each other.

When the light waves pass through the slit, they spread or diverge. The waves then overlap and interfere with each other (constructive interference). The result is that some places on the screen appear brighter than others.

Single slit diffraction graph.
A diagrammatical representation of single slit diffraction.

The pattern formed by single-slit diffraction depends on how far away you are from the screen where you see it.

  • If you are very close to the screen, then each wave will hit it before it can spread out very far in all directions from its original spot.
  • But if you move farther away from the screen, more and more waves will be able to spread out before hitting it again.
  • So if you want to see this effect clearly, moving farther away from whatever object is causing it is best!

What Is Double Slit Diffraction?

Double-slit diffraction is a phenomenon that occurs when light passes through two slits. When this happens, the light spreads out into a shape called an interference pattern. This pattern comprises an infinite number of overlapping waves, and each wave has its wavelength.

The interference pattern is also made up of bright spots where the waves overlap constructively (they add together) and dark spots where they overlap destructively (subtracting from each other). The wavelength of each wave is related to its frequency—the more waves that overlap in a given spot, the higher the frequency will be in that spot.

To understand how this works, imagine standing at a train crossing with tracks on either side of you. A single train arrives on one track and crosses your path; another arrives on the other track and crosses your path. You’ll see two trains go by.

Imagine three trains arriving at once—one on each track—and they cross paths right before you! You’ll see six trains go by instead: three sets of two trains each time they cross paths with one another (one set going eastward.

Difference Between Single Slit And Double Slit Diffraction

Single-slit diffraction and double-slit diffraction are ways to observe light wave properties.

In single-slit diffraction, a single slit is used to illuminate a screen, and the pattern formed by the light reflected from it is observed. In contrast, two slits illuminate a screen in double-slit diffraction, and the pattern formed by the light reflected from it is observed.

  • In single-slit diffraction, only one wave passes through the slit at any given time, so each point on the screen will receive one wave at a time.
  • In double-slit diffraction, however, we see two lines or spots of light simultaneously—one for each wave that passes through both slits simultaneously.
  • Single-slit diffraction creates a chevron pattern, while double-slit diffraction creates an interference pattern.
  • Single-slit diffraction has sharp edges between bright and dark regions, while double-slit diffraction has smooth edges between bright and dark regions.
  • In single-slit diffraction, the intensity pattern shows no structure other than the central maximum and surrounding fringes.
  • In double-slit diffraction, the intensity pattern shows a series of maxima and minima in addition to those caused by double slits.

You can also study these differences in this table.

Single Slit DiffractionDouble Slit Diffraction
It has only one slit for the passage of light.It has two holes for the passage of light.
Only a single ray of light can pass at a time in this process.Two rays of light pass simultaneously in this process.
No visible structure pattern at the other end of the light is observed.An organized structure pattern is observed at the other end of the light.
It creates a chevron pattern.It creates an interference pattern.
Differences between the single slit and double slit diffraction.

Here is a video explaining the differences between single-slit and double-slit diffraction.

Single-slit and double-slit diffraction experiment.

What’s The Formula For Diffraction?

The formula of diffraction is as follows;

dsin0=nλ where

  • d is the distance between the slits.
  • 0 is the diffraction angle.
  • n is the order number of maximum.
  • And λ is the wavelength of light.

What Are The Two Types Of Diffraction?

There are two types of diffraction: constructive and destructive.

Constructive diffraction occurs when the incident light is greater than the critical angle. This means the light waves can pass through the object and continue on its path, creating a series of images known as a diffraction pattern.

Image of double rainbow.
Rainbow forms due to versatile patterns of light traveling through different mediums.

Destructive diffraction occurs when the incident light is less than the critical angle. In this case, each interface between air and glass (or other material) reflects some of the light waves. These reflections combine to form a symmetrical pattern about both axes (horizontal and vertical).

What Is Interference?

Interference is the phenomenon where two waves interact to produce a resultant wave with a different amplitude and frequency than the individual waves.

When two waves of the same frequency come together, they produce a new wave with twice the amplitude. This is called constructive interference.

If the two waves have different frequencies but are still close enough in frequency that they can be superimposed, they will interfere constructively when they are in phase (they will have the same phase) and destructively when out of phase.

Final Thoughts

  • Single-slit and double-slit diffraction are different ways to view the same phenomenon.
  • The first is a single slit where light passes through one opening in an opaque material, whereas the second is a double slit where light passes through two openings in an opaque material.
  • The diffraction pattern consists of alternating light and dark bands caused by constructive and destructive interference in a double-slit experiment.
  • In contrast, the single-slit diffraction experiment involves only one slit and produces a single dark band that appears on the screen where the slit is located.
  • In the case of single-slit diffraction, only one wave passes through the slit.
  • In the case of double-slit diffraction, two waves pass through each slit.

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